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

Why it is Amber

• CVSS 8.1 high
• Public exploit or proof of concept referenced
• On your watchlist: Go

Affected packages

References

• https://github.com/advisories/GHSA-vvcv-vpph-h844
• https://github.com/go-vikunja/vikunja/security/advisories/GHSA-vvcv-vpph-h844
• https://nvd.nist.gov/vuln/detail/CVE-2026-68581
• https://github.com/go-vikunja/vikunja/commit/95b7e673fb5ee407498fa4b13e8b4c57847a4a0b
• https://github.com/go-vikunja/vikunja/commit/e6b25bd57b537ef9a72b5acdadf446ca5ef77bfa
• https://github.com/go-vikunja/vikunja/releases/tag/v2.4.0
• https://www.vulncheck.com/advisories/vikunja-through-authentication-bypass-via-principal-id-collision
• https://github.com/advisories/GHSA-vvcv-vpph-h844

Original description

Vikunja versions 0.22.0 through 2.3.0 fail to validate the principal type in API token management. Because user IDs and link-share IDs are independent numeric sequences and both resolve through a generic web.Auth.GetID() interface, a link-share JWT whose numeric ID equals a target user's ID is treated as that user by the /api/v1/tokens endpoints. An authenticated attacker can obtain a target's numeric user ID via authenticated user search, then create link shares on an attacker-writable project until the link-share sequence reaches that value, and use the resulting link-share JWT to list, create, and delete the target user's API tokens (including issuing a new token with attacker-chosen scopes under the target's permissions). Fixed in version 2.4.0.