Budibase auth session cookies are set with httpOnly:false — any XSS can lead to full account takeover

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.1 · CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-42239: 0.28% estimated exploitation activity in the next 30 days; percentile 20.94 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The budibase:auth cookie containing the JWT session token is set with httpOnly: false at packages/backend-core/src/utils/utils.ts:218. JavaScript can read this cookie via document.cookie. Given that Budibase has had XSS vulnerabilities (GHSA-gp5x-2v54-v2q5 — stored XSS via unsanitized entity names, published April 2, 2026), this means every XSS becomes a full account takeover — the attacker steals the JWT and has persistent access to the victim's account. The cookie also lacks secure: true (sent over plaintext HTTP) and sameSite attribute. Details packages/backend-core/src/utils/utils.ts, lines 215-226: This function is called for setting the budibase:auth cookie which contains the signed JWT session token. With httpOnly: false, any JavaScript execution context (XSS, injected script, browser extension) can read the token via document.cookie. Missing flags: - httpOnly: false → should be true (prevent JS access) - No secure flag → cookie sent over HTTP (should be secure: true…

Published by the source

24 Apr 2026, 16:18 UTC

Last modified by the source

11 May 2026, 13:53 UTC

Source last checked

26 Oct 2026, 12:51 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4f9j-vr4p-642r

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-4f9j-vr4p-642r

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# Patch Next advisory brief: CVE-2026-42239

Advisory: Budibase auth session cookies are set with httpOnly:false — any XSS can lead to full account takeover
IDs: CVE-2026-42239, GHSA-4f9j-vr4p-642r
Record: https://patchnext.com/advisories/cve-2026-42239 (revision 2, source checked 26 Oct 2026, 12:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @budibase/backend-core 3.35.10. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @budibase/backend-core: affected < 3.35.10; fixed in 3.35.10

## Suggested inspection (read-only)
- `npm ls @budibase/backend-core --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @budibase/backend-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-4f9j-vr4p-642r (OSV record GHSA-4f9j-vr4p-642r lists affected ranges: npm @budibase/backend-core >=0 <3.35.10 (fixed))
- Verified: https://github.com/advisories/GHSA-4f9j-vr4p-642r (GitHub-reviewed advisory GHSA-4f9j-vr4p-642r lists affected ranges: npm @budibase/backend-core >=0 <3.35.10)

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