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Description

Vikunja before 2.2.1 contains an authorization flaw where the LinkSharing.ReadAll endpoint exposes share hashes to users with read access, enabling permission escalation to admin-level shares. The GetTaskAttachment endpoint performs permission checks against user-supplied task IDs but fetches attachments by sequential ID without verifying ownership, allowing attackers to download and delete all file attachments across all projects instance-wide.

PUBLISHED Reserved 2026-06-22 | Published 2026-07-10 | Updated 2026-07-10 | Assigner VulnCheck




CRITICAL: 9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CRITICAL: 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem types

Authorization Bypass Through User-Controlled Key

Product status

Default status
unaffected

Any version before 2.2.1
affected

2.2.1 (semver)
unaffected

Credits

offset reporter

References

github.com/...ikunja/security/advisories/GHSA-2pv8-4c52-mf8j exploit

github.com/...ikunja/security/advisories/GHSA-2pv8-4c52-mf8j (GitHub Security Advisory (GHSA-2pv8-4c52-mf8j)) vendor-advisory

www.vulncheck.com/...ined-with-cross-project-attachment-idor (VulnCheck Advisory: Vikunja - Unauthenticated Instance-Wide Data Breach via Link Share Hash Disclosure Chained with Cross-Project Attachment IDOR) third-party-advisory

cve.org (CVE-2026-56765)

nvd.nist.gov (CVE-2026-56765)

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