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GHSA-v479-vf79-mg83

MEDIUMFix: go-vikunja/vikunja#2584

GHSA-v479-vf79-mg83 is a medium-severity (CVSS 5.4) CWE-836 vulnerability in code.vikunja.io/api. O3 Security confirms whether GHSA-v479-vf79-mg83 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

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

Also known asCVE-2026-40103GO-2026-5650
Published
Apr 10, 2026
Updated
Jun 25, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for GHSA-v479-vf79-mg83.

Real-World Exposure

1 pkg affected
🐹code.vikunja.io/api

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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.background_delete is rejected.

This is a scoped-token authorization bypass.

Details

I verified this locally on commit c5450fb55f5192508638cbb3a6956438452a712e.

Relevant code paths:

  • pkg/models/api_routes.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.background_delete

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 stored route detail.

This matters because RemoveProjectBackground() is a real destructive operation:

  • It checks project update rights.
  • It deletes the background file if present.
  • It clears the project's BackgroundFileID.

PoC

  1. Log in as a user who can update a project that already has a background.
  2. Create an API token with only: {"projects":["background"]}
  3. Send: DELETE /api/v1/projects/<project_id>/background Authorization: Bearer <token>
  4. Observe that the request succeeds and the project background is removed.

For comparison:

  1. Create an API token with only: {"projects":["background_delete"]}
  2. Repeat the same DELETE request.
  3. Observe that the request is rejected with 401 Unauthorized.

I confirmed this locally with three validations:

  1. /api/v1/routes advertises both background and background_delete.
  2. The matcher unit test proves CanDoAPIRoute() accepts DELETE for background.
  3. The webtest proves a real API token with only background successfully deletes the background.

Impact

Scoped API tokens can exceed their intended capability. A token intended for project background access can delete project backgrounds, which weakens the trust model for automation and third-party integrations that rely on narrowly scoped tokens.

The attacker needs a valid API token created by a user who has update rights on the target project, but the token itself only needs the weaker projects.background permission.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gocode.vikunja.io/apiall versions2.3.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for code.vikunja.io/api. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update code.vikunja.io/api to 2.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v479-vf79-mg83 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether GHSA-v479-vf79-mg83 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-v479-vf79-mg83. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### 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.background_delete` is rejected. This is a scoped-token authorization bypass. ### Details I verified this locally on commit `c5450fb55f5192508638cbb3a6956438452a712e`. Relevant code paths: * `pkg/models/api_routes.go` * `pkg/routes/routes.go` * `pkg/modules/background/handler/background.go` Route registration exposes separate permissions for the same path: * `GET /
O3 Security · Impact-Aware SCA

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