Vikunja: Scoped API tokens with projects.background permission can delete project backgrounds

Exploitation

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

CVSS

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

EPSS

• CVE-2026-40103: 0.22% estimated exploitation activity in the next 30 days; percentile 12.89 (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 Vikunja's scoped API token enforcement for custom project background routes is method-confused. A token with only projects.background can successfully delete a project background, while a token with only projects.backgrounddelete is rejected. This is a scoped-token authorization bypass. Details I verified this locally on commit c5450fb55f5192508638cbb3a6956438452a712e. Relevant code paths: pkg/models/apiroutes.go pkg/routes/routes.go pkg/modules/background/handler/background.go Route registration exposes separate permissions for the same path: GET /api/v1/projects/:project/background - projects.background DELETE /api/v1/projects/:project/background - projects.backgrounddelete At enforcement time, CanDoAPIRoute() falls back to the parent group and reconstructs the child permission from the path segments only. For the DELETE request, that becomes background, so the matcher accepts any token containing projects.background without re-checking the HTTP method or matching the…

Published by the source

10 Apr 2026, 15:36 UTC

Last modified by the source

24 Apr 2026, 20:49 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-v479-vf79-mg83

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# Patch Next advisory brief: CVE-2026-40103

Advisory: Vikunja: Scoped API tokens with projects.background permission can delete project backgrounds
IDs: CVE-2026-40103, GHSA-v479-vf79-mg83
Record: https://patchnext.com/advisories/cve-2026-40103 (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: code.vikunja.io/api 2.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.vikunja.io/api: affected < 2.3.0; fixed in 2.3.0

## Suggested inspection (read-only)
- Go code.vikunja.io/api: check the installed version with your package manager.

## 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 code.vikunja.io/api.
- 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-v479-vf79-mg83 (GitHub-reviewed advisory GHSA-v479-vf79-mg83 lists affected ranges: Go code.vikunja.io/api >=0 <2.3.0)

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