CVE-2026-68581

Deferred Deferred - Pending Action

Authentication Bypass in Vikunja via ID Collision

Publication date: 2026-08-02

Last updated on: 2026-10-23

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

2026-10-23

Generated

2026-11-08

AI Q&A

2026-08-02

EPSS Evaluated

2026-11-07

NVD

CVE-2026-68581

EUVD

EUVD-2026-51991

Affected Vendors & Products

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

KEV

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

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.

Detection Guidance

This vulnerability requires manual verification as it involves API token management flaws in Vikunja. Check Vikunja versions between 0.22.0 and 2.3.0 for exposure. Review API token logs for unauthorized token creation or deletion events. Inspect JWT tokens for link-share IDs matching user IDs.

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.

Compliance Impact

This vulnerability could lead to unauthorized access to user API tokens, potentially exposing sensitive data. For GDPR, this may violate principles of data protection and user consent. For HIPAA, it risks unauthorized access to protected health information if tokens grant access to such data.

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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