CVE-2026-91985
Received Received - Intake

Vikunja Access Control Bypass via Link-Share Hash Exposure

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: VulnCheck

Description
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.

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Meta Information

Published
2026-09-15
Last Modified
2026-09-15
Generated
2026-09-15
AI Q&A
2026-09-15
EPSS Evaluated
N/A
NVD
CVE-2026-91985
EUVD
EUVD-2026-78656

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
vikunja vikunja to 2.6.0 (exc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-200 The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.

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Executive Summary

Vikunja before version 2.6.0 has a flaw where read-only members can access a link-share's secret credential through single-share read endpoints. This allows them to escalate their permissions by exchanging the hash for a higher-privilege token, enabling unauthorized actions like writing or administrative tasks.

Detection Guidance

To detect this vulnerability, check if your Vikunja instance is running a version before 2.6.0. Use commands like 'curl -s https://your-vikunja-instance/api/v1/info | grep version' to verify the version. If the version is below 2.6.0, the system is vulnerable.

Impact Analysis

If you use Vikunja versions before 2.6.0, an attacker with read-only access could gain elevated privileges. This could lead to unauthorized data modification, task creation, or administrative changes, potentially compromising your project data or system integrity.

Compliance Impact

This vulnerability could lead to unauthorized access and data exposure, violating GDPR's data protection principles or HIPAA's security requirements. It may result in non-compliance due to broken access controls and potential information leaks.

Mitigation Strategies

Immediately upgrade Vikunja to version 2.6.0 or later. If upgrading is not possible, restrict access to single-share read endpoints by modifying server configurations to enforce admin-only access to the hash field.

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