Vikunja: Read-only project members can obtain any link share's access hash via the single-share read endpoint (v1 and v2) and escalate to the share's permission level

Exploitation

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

CVSS

not scored

EPSS

• CVE-2026-91985: 0.43% estimated exploitation activity in the next 30 days; percentile 37.54 (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 A user who has only read permission on a project can call the single link-share read endpoint and receive the share's hash field — the secret credential that the anonymous POST /shares/{share}/auth endpoint exchanges for a link-share JWT carrying the share's permission (read / read-write / admin). A read-only member can therefore mint a write- or admin-level token for the project and perform writes they are not entitled to, while their own user token is correctly refused. This is the remaining variant of the link-share hash disclosure class: GHSA-8hp8-9fhr-pfm9 fixed the list endpoint (ReadAll now requires project admin) but the single-read endpoint's gate was never aligned. Verified on Vikunja 2.5.0; the weak gate has existed since the endpoint, so earlier versions are likely affected too. Details Affected endpoints (both verified with a complete chain): - v1: GET /api/v1/projects/{project}/shares/{share} - v2: GET /api/v2/projects/{project}/shares/{share} Permission gate:…

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 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-qfwc-vx6f-3g6g

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6747

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-qfwc-vx6f-3g6g

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# Patch Next advisory brief: CVE-2026-91985

Advisory: Vikunja: Read-only project members can obtain any link share's access hash via the single-share read endpoint (v1 and v2) and escalate to the share's permission level
IDs: CVE-2026-91985, GHSA-qfwc-vx6f-3g6g
Record: https://patchnext.com/advisories/cve-2026-91985 (revision 3, 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: Unrated
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-2026-6747 (OSV record GO-2026-6747 lists affected ranges: Go code.vikunja.io/api >=0)
- Verified: https://osv.dev/vulnerability/GHSA-qfwc-vx6f-3g6g (OSV record GHSA-qfwc-vx6f-3g6g lists affected ranges: Go code.vikunja.io/api >=0 <2.6.0 (fixed))
- Verified: https://github.com/advisories/GHSA-qfwc-vx6f-3g6g (GitHub-reviewed advisory GHSA-qfwc-vx6f-3g6g lists affected ranges: Go code.vikunja.io/api >=0 <=2.5.0)

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