EUVD-2026-21417
GHSA-96q5-xm3p-7m84
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Lifecycle Timeline
4Description
Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, Vikunja's link share authentication (GetLinkShareFromClaims in pkg/models/link_sharing.go) constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl). This vulnerability is fixed in 2.3.0.
Analysis
Vikunja prior to version 2.3.0 fails to validate link share permissions against server state during JWT authentication, allowing attackers with revoked or downgraded JWT tokens to maintain the original access level for up to 72 hours. This affects self-hosted task management deployments where link shares are used for collaboration, enabling unauthorized information disclosure and modification of shared projects even after a project owner explicitly revokes or restricts access.
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External POC / Exploit Code
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