CVE-2026-55066

A vulnerability in Vikunja before version 2.2.1 allows unauthorized access to share hashes and downloading/deleting all file attachments across the instance. An authorization flaw in the LinkSharing.ReadAll and GetTaskAttachment endpoints enables privilege escalation to admin-level shares.

Vikunja versions prior to 2.4.0 store password-reset, email-confirmation, and account-deletion tokens in the user_tokens table in plaintext. An attacker with read access to the database can immediately use pending tokens to take over user accounts without knowing passwords. Version 2.4.0 fixes the issue.

Vikunja versions 1.0.0 through 2.3.0, when an administrator enables the per-provider emailfallback option on an OpenID Connect provider, links an SSO login to a pre-existing local account using only the email claim from the IdP, without checking email_verified or requiring the account password. An attacker with a token carrying a victim's email can log in as that victim without consent. Version 2.4.0 fixes the issue.

Vikunja version 2.3.0 allows a scoped API token limited to the oauth.authorize permission to call POST /api/v1/oauth/authorize, obtain an OAuth authorization code, and exchange it for a normal bearer JWT and refresh token. The resulting credentials are not restricted by the original token's permissions, granting access to routes outside its declared scope. Version 2.4.0 fixes the vulnerability.

Vikunja before 2.6.0 fails to properly restrict access to the link-share hash field in single-share read endpoints, allowing read-only members to obtain the share's secret credential. Attackers can exchange the disclosed hash for a link-share JWT at the share's permission level to escalate privileges and perform unauthorized writes or administrative actions.

Vikunja before 2.6.0 fails to validate that user-supplied project_view_id in task-position requests belongs to the task's project. Authenticated attackers can insert task position rows into arbitrary other tenant project views via POST or PUT task-position endpoints.

Vikunja before 2.6.0 contains an API token scope bypass vulnerability in task read endpoints where authorization fails to inspect query string parameters. Attackers with limited token scopes can use the expand parameter to access restricted data like comments, reactions, and time entries without proper permission verification.

Vikunja before 2.6.0 continues to expose the raw TOTP shared secret after enrollment through the GET /api/v1/user/settings/totp and /api/v1/user/settings/totp/qrcode endpoints without re-authentication. Attackers with a valid access token can read the secret, import it into their own authenticator, and generate valid codes indefinitely to defeat the second factor and enable account takeover.

Vikunja versions before 2.6.0 fail to properly validate link-share tokens in the v2 API user search endpoints. Attackers with a read-only share link can enumerate project users via the projects endpoint and confirm arbitrary usernames exist via the global search endpoint.

vikunja before 2.6.0 fails to validate team access when attaching teams to projects, allowing authenticated users to enumerate all teams and members. Attackers can attach arbitrary team IDs via the project teams endpoint to retrieve complete team rosters including member names and admin flags for unauthorized teams.