Vikunja: Link-share principal ID collision allows cross-account API token issuance and management

Exploitation

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

CVSS

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

EPSS

• CVE-2026-68581: 0.46% estimated exploitation activity in the next 30 days; percentile 40.23 (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.

Executive Summary Vikunja accepts both regular-user JSON Web Tokens (JWTs) and link-share JWTs through its generic authenticated API route group. A link-share JWT resolves to a models.LinkSharing principal whose GetID() method returns the numeric linkshares.id. The API-token management model then treats that generic numeric value as a users.id when it creates, lists, and deletes API tokens. Because users.id and linkshares.id are independent positive sequences, a link share whose ID equals another user's ID is treated as that user by /api/v1/tokens. An ordinary authenticated attacker can obtain a target's numeric user ID through authenticated user search and create link shares on an attacker-writable project until the link-share sequence reaches that value. The colliding link-share principal can then list the target's API-token metadata, issue a new API token owned by the target, and delete target-owned API tokens. The newly issued token operates with attacker-selected valid API…

Published by the source

9 Oct 2026, 20:42 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-vvcv-vpph-h844

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6753

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-vvcv-vpph-h844

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# Patch Next advisory brief: CVE-2026-68581

Advisory: Vikunja: Link-share principal ID collision allows cross-account API token issuance and management
IDs: CVE-2026-68581, GHSA-vvcv-vpph-h844
Record: https://patchnext.com/advisories/cve-2026-68581 (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: High (CVSS 8.1)
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 2.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.vikunja.io/api: affected >= 0.22.0, <= 2.3.0; fixed in 2.4.0

## 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-2026-6753 (OSV record GO-2026-6753 lists affected ranges: Go code.vikunja.io/api >=0.22.0)
- Verified: https://osv.dev/vulnerability/GHSA-vvcv-vpph-h844 (OSV record GHSA-vvcv-vpph-h844 lists affected ranges: Go code.vikunja.io/api >=0.22.0 <2.4.0 (fixed))
- Verified: https://github.com/advisories/GHSA-vvcv-vpph-h844 (GitHub-reviewed advisory GHSA-vvcv-vpph-h844 lists affected ranges: Go code.vikunja.io/api >=0.22.0 <=2.3.0)

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