CVE-2026-68581
Received Received - Intake

Authentication Bypass in Vikunja via ID Collision

Publication date: 2026-08-02

Last updated on: 2026-08-02

Assigner: VulnCheck

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.

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Meta Information

Published
2026-08-02
Last Modified
2026-08-02
Generated
2026-08-02
AI Q&A
2026-08-02
EPSS Evaluated
N/A
NVD
CVE-2026-68581
EUVD
EUVD-2026-51991

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
vikunja vikunja From 0.22.0 (inc) to 2.3.0 (inc)
vikunja vikunja 2.4.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-863 The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Attack-Flow Graph

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Executive Summary

Vikunja versions 0.22.0 through 2.3.0 have a flaw in API token management where user IDs and link-share IDs are not properly validated. An attacker can exploit this by creating a link-share JWT with an ID matching a target user's ID, allowing them to impersonate that user and manipulate API tokens.

Impact Analysis

An authenticated attacker could list, create, or delete your API tokens, including issuing new tokens with elevated privileges under your identity. This could lead to unauthorized access to your data and actions within the system.

Mitigation Strategies

Immediately upgrade Vikunja to version 2.4.0 or later to patch the vulnerability. Review API token permissions and revoke any suspicious tokens. Monitor for unauthorized token creation or access.

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