GHSA-2pv8-4c52-mf8j
Critical · 9.1Vikunja: Unauthenticated Instance-Wide Data Breach via Link Share Hash Disclosure Chained with Cross-Project Attachment IDOR
CVSS
9.1
EPSS
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Published
Mar 26, 2026
CISA due date
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The record
Two independently-exploitable authorization flaws in Vikunja can be chained to allow an unauthenticated attacker to download and delete every file attachment across all projects in a Vikunja instance. The `ReadAll` endpoint for link shares exposes share hashes (including admin-level shares) to any user with read access, enabling permission escalation. The task attachment `ReadOne`/`GetTaskAttachment` endpoint performs permission checks against a user-supplied task ID but fetches the attachment by its own sequential ID without verifying the attachment belongs to that task, enabling cross-project file access.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|
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