Vikunja: Cross-tenant task-position rows can be injected into arbitrary project views via the unvalidated project_view_id in the task position endpoint (v1 and v2)

Exploitation

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

CVSS 4.0

5.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-91984: 0.26% estimated exploitation activity in the next 30 days; percentile 18.38 (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 task-position endpoint authorizes only the task side of the write: TaskPosition.CanUpdate delegates to Task.CanUpdate (write access to the task's own project) and the request body's projectviewid is never validated to belong to the task's project, nor is any access to that view required. Any authenticated user with a single writable task of their own can persist (taskid, projectviewid, position) rows into any other tenant's project view (view IDs are small sequential integers and enumerable). Low position values (below MinPositionSpacing, 0.01) enter the recalculation branch, but RecalculateTaskPositions aborts on its own project read-access check before recalculating and the whole transaction rolls back, so no cross-tenant recalculation actually executes — only the plain row insert (position ≥ 0.01) persists. This is the same root-cause pattern as GHSA-569v-q83c-3j3g (kanban bucket relocation via projectviewid mass-assignment, fixed with a dual-side check for buckets in…

Published by the source

9 Oct 2026, 20:51 UTC

Last modified by the source

19 Oct 2026, 21:31 UTC

Source last checked

26 Oct 2026, 15:32 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w39f-h553-h2mx

2. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6755

4. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w39f-h553-h2mx

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# Patch Next advisory brief: CVE-2026-91984

Advisory: Vikunja: Cross-tenant task-position rows can be injected into arbitrary project views via the unvalidated project_view_id in the task position endpoint (v1 and v2)
IDs: CVE-2026-91984, GHSA-w39f-h553-h2mx
Record: https://patchnext.com/advisories/cve-2026-91984 (revision 4, source checked 26 Oct 2026, 15:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
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 2.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.vikunja.io/api: affected <= 2.5.0; fixed in 2.6.0

## 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://osv.dev/vulnerability/GO-2026-6755 (OSV record GO-2026-6755 lists affected ranges: Go code.vikunja.io/api >=0)
- Verified: https://osv.dev/vulnerability/GHSA-w39f-h553-h2mx (OSV record GHSA-w39f-h553-h2mx lists affected ranges: Go code.vikunja.io/api >=0 <2.6.0 (fixed))
- Verified: https://github.com/advisories/GHSA-w39f-h553-h2mx (GitHub-reviewed advisory GHSA-w39f-h553-h2mx lists affected ranges: Go code.vikunja.io/api >=0 <=2.5.0)

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