Memory-safety vulnerability in github.com/jackc/pgx/v5.

IBM Concert

@isaacs/brace-expansion is a hybrid CJS/ESM TypeScript fork of brace-expansion. Prior to version 5.0.1, @isaacs/brace-expansion is vulnerable to a denial of service (DoS) issue caused by unbounded brace range expansion. When an attacker provides a pattern containing repeated numeric brace ranges, the library attempts to eagerly generate every possible combination synchronously. Because the expansion grows exponentially, even a small input can consume excessive CPU and memory and may crash the Node.js process. This issue has been patched in version 5.0.1.

Summary A prototype pollution vulnerability exists in the the npm package swiper (>=6.5.1, < 12.1.2). Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using Array.prototype. The exploit works across Windows and Linux and on Node and Bun runtimes. This issue is fixed in version 12.1.2

Details The vulnerability resides in line 94 of shared/utils.mjs where indexOf() function is used to check whether user provided input contain forbidden strings.

PoC Steps to reproduce 1. Install latest version of swiper using npm install 2. Run the following code snippet: javascript var swiper = require('swiper'); Array.prototype.indexOf = () => -1; let obj = {}; var maliciouspayload = '{"proto":{"polluted":"yes"}}'; console.log({}.polluted); swiper.default.extendDefaults(JSON.parse(maliciouspayload)); console.log({}.polluted); // prints yes -> indicating that the patch was bypassed and prototype pollution occurred

Expected behavior Prototype pollution should be prevented and {} should not gain new properties. This should be printed on the console: undefined undefined OR throw an Error

Actual behavior Object.prototype is polluted This is printed on the console: undefined yes

Impact This is a prototype pollution vulnerability, which can have severe security implications depending on how swiper is used by downstream applications. Any application that processes attacker-controlled input using this package may be affected. It could potentially lead to the following problems: 1. Authentication bypass 2. Denial of service - Even if an attacker is not able to exploit prototype pollution in swiper, if there is a prototype pollution within the project from other dependencies, modifying global Array.prototype.indexOf property can result in crash when swiper.default.extendDefaults is called because swiper makes use of this global property. This can lead to Denial of Service. 3. Remote code execution (if polluted property is passed to sinks like eval or childprocess)

Related CVEs CVE-2026-25521 CVE-2026-25047 CVE-2026-26021

The basic-ftp FTP client library for Node.js contains a path traversal vulnerability (CWE-22) in versions prior to 5.2.0 in the downloadToDir() method. A malicious FTP server can send directory listings with filenames containing path traversal sequences (../) that cause files to be written outside the intended download directory. Version 5.2.0 patches the issue.

GHSA-fw9q-39r9-c252: Prototype Pollution via Incomplete Lodash set() Guard in langsmith-sdk

Severity: Medium (CVSS ~5.6) Status: Fixed in 0.5.18

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Summary

The LangSmith JavaScript/TypeScript SDK (langsmith) contains an incomplete prototype pollution fix in its internally vendored lodash set() utility. The baseAssignValue() function only guards against the proto key, but fails to prevent traversal via constructor.prototype. This allows an attacker who controls keys in data processed by the createAnonymizer() API to pollute Object.prototype, affecting all objects in the Node.js process.

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Affected Products

| Product | Affected Versions | Component | |---------|-------------------|-----------| | langsmith (npm) | <= 0.5.17 | js/src/utils/lodash/baseAssignValue.ts, js/src/anonymizer/index.ts | | langchain-ai/langsmith-sdk | GitHub main branch (as of 2026-03-24) | JS/TypeScript SDK |

Not affected: The Python SDK (langsmith on PyPI) does not use lodash or an equivalent pattern.

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Root Cause

The SDK vendors an internal copy of lodash's set() function at js/src/utils/lodash/. The baseAssignValue() function at baseAssignValue.ts:11 implements a guard for prototype pollution:

typescript function baseAssignValue(object: Record<string, any>, key: string, value: any) { if (key === "proto") { Object.defineProperty(object, key, { configurable: true, enumerable: true, value: value, writable: true, }); } else { object[key] = value; // ← No guard for "constructor" or "prototype" keys } }

This blocks proto pollution but does not block the constructor.prototype traversal path. When set() is called with a path like "constructor.prototype.polluted":

1. castPath() splits it into ["constructor", "prototype", "polluted"] 2. baseSet() iterates: obj.constructor → Object → Object.prototype 3. assignValue(Object.prototype, "polluted", value) calls baseAssignValue() 4. Key is "polluted" (not "proto"), so the guard is bypassed 5. Object.prototype.polluted = value — all objects are polluted

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Attack Vector via Anonymizer

The createAnonymizer() API (importable as langsmith/anonymizer) processes data by:

1. Extracting string nodes — extractStringNodes() walks an object recursively and builds dotted paths from keys 2. Applying regex replacements — If a string value matches a configured pattern, the node is marked for update (anonymizer/index.ts:95) 3. Writing back with set() — set(mutateValue, node.path, node.value) writes the replaced value back (anonymizer/index.ts:123)

An attacker who controls keys in data being anonymized can construct a nested object where the path resolves to constructor.prototype.X:

javascript { wrapper: { "constructor.prototype.isAdmin": "contains-secret-pattern" } }

extractStringNodes() produces path "wrapper.constructor.prototype.isAdmin". When the replacement triggers and set() writes back, it traverses up to Object.prototype.

Although createAnonymizer() uses deepClone() at anonymizer/index.ts:62 (JSON.parse(JSON.stringify(data))), the prototype chain traversal escapes the clone boundary because clone.wrapper.constructor resolves to the global Object constructor, not a cloned copy.

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Proof of Concept

javascript import { createAnonymizer } from "langsmith/anonymizer";

const anonymizer = createAnonymizer([ { pattern: "secret", replace: "[REDACTED]" } ]);

console.log("BEFORE:", ({}).isAdmin); // undefined

const maliciousInput = { wrapper: { "constructor.prototype.isAdmin": "this-is-secret-data" } };

anonymizer(maliciousInput);

console.log("AFTER:", ({}).isAdmin); // "this-is-[REDACTED]-data" console.log("Array:", [].isAdmin); // "this-is-[REDACTED]-data"

function checkAccess(user) { if (user.isAdmin) return "ACCESS GRANTED"; return "ACCESS DENIED"; } console.log(checkAccess({ name: "bob" })); // "ACCESS GRANTED" ← BYPASSED

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Impact

Prototype pollution in a Node.js process can enable:

1. Authentication bypass — if (user.isAdmin) checks succeed on all objects 2. Remote Code Execution — Exploitable in template engines (Pug, EJS, Handlebars, Nunjucks) via polluted prototype properties that reach eval()/Function() sinks 3. Denial of Service — Overwriting toString, valueOf, or hasOwnProperty on all objects 4. Data exfiltration — Polluting serialization methods to inject attacker-controlled values

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Remediation

In baseAssignValue.ts, extend the guard to cover constructor and prototype keys:

typescript function baseAssignValue(object, key, value) { if (key === "proto" || key === "constructor" || key === "prototype") { Object.defineProperty(object, key, { configurable: true, enumerable: true, value, writable: true, }); } else { object[key] = value; } }

As defense in depth, extractStringNodes() in anonymizer/index.ts should also sanitize or reject path segments matching constructor or prototype before passing them to set().

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Timeline

| Date | Event | |------|-------| | 2026-03-24 | Initial report submitted | | 2026-04-09 | Vendor confirmed; fixed in 0.5.18 |

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Credits

Reported by: OneThing4101