Budibase: Authentication Bypass via Unanchored Regex in Public Endpoint Matcher — Unauthenticated Access to Protected Endpoints

Exploitation

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

CVSS

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

EPSS

• CVE-2026-41428: 0.45% estimated exploitation activity in the next 30 days; percentile 38.74 (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 authenticated middleware uses unanchored regular expressions to match public (no-auth) endpoint patterns against ctx.request.url. Since ctx.request.url in Koa includes the query string, an attacker can access any protected endpoint by appending a public endpoint path as a query parameter. For example, POST /api/global/users/search?x=/api/system/status bypasses all authentication because the regex /api/system/status/ matches in the query string portion of the URL. Details Step 1 — Public endpoint patterns compiled without anchors packages/backend-core/src/middleware/matchers.ts, line 26: No ^ prefix, no $ suffix. The regex matches anywhere in the test string. Step 2 — Regex tested against full URL including query string packages/backend-core/src/middleware/matchers.ts, line 32: Koa's ctx.request.url returns the full URL including query string (e.g., /api/global/users/search?x=/api/system/status). The regex /api/system/status matches in the query string. Step 3 —…

Published by the source

16 Apr 2026, 22:40 UTC

Last modified by the source

5 May 2026, 16:11 UTC

Source last checked

26 Oct 2026, 12:51 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8783-3wgf-jggf

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-8783-3wgf-jggf

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-8783-3wgf-jggf

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# Patch Next advisory brief: CVE-2026-41428

Advisory: Budibase: Authentication Bypass via Unanchored Regex in Public Endpoint Matcher — Unauthenticated Access to Protected Endpoints
IDs: CVE-2026-41428, GHSA-8783-3wgf-jggf
Record: https://patchnext.com/advisories/cve-2026-41428 (revision 3, 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: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @budibase/backend-core: affected <= 3.35.3

## 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
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## 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://github.com/advisories/GHSA-8783-3wgf-jggf (GitHub-reviewed advisory GHSA-8783-3wgf-jggf lists affected ranges: npm @budibase/backend-core >=0 <=3.35.3)
- Verified: https://osv.dev/vulnerability/GHSA-8783-3wgf-jggf (OSV record GHSA-8783-3wgf-jggf lists affected ranges: npm @budibase/backend-core >=0 <=3.35.3)

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