Vikunja: Unauthenticated Instance-Wide Data Breach via Link Share Hash Disclosure Chained with Cross-Project Attachment IDOR

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary 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. Details Vulnerability 1: Link Share Hash Disclosure (Permission Escalation Entry Point) Tracked in https://github.com/go-vikunja/vikunja/security/advisories/GHSA-8hp8-9fhr-pfm9 The LinkSharing.ReadAll() method in pkg/models/linksharing.go:228-287 returns all link shares for a project, including the Hash field: The ReadAll clears passwords but not hashes: A link share user with…

Published by the source

26 Mar 2026, 16:56 UTC

Last modified by the source

26 Mar 2026, 16:56 UTC

Source last checked

26 Oct 2026, 15:18 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2pv8-4c52-mf8j

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# Patch Next advisory brief: GHSA-2pv8-4c52-mf8j

Advisory: Vikunja: Unauthenticated Instance-Wide Data Breach via Link Share Hash Disclosure Chained with Cross-Project Attachment IDOR
IDs: GHSA-2pv8-4c52-mf8j
Record: https://patchnext.com/advisories/ghsa-2pv8-4c52-mf8j (revision 1, source checked 26 Oct 2026, 15:18 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: code.vikunja.io/api 2.2.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.vikunja.io/api: affected <= 2.2.0; fixed in 2.2.1

## Suggested inspection (read-only)
- Go code.vikunja.io/api: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on code.vikunja.io/api.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2pv8-4c52-mf8j (GitHub-reviewed advisory GHSA-2pv8-4c52-mf8j lists affected ranges: Go code.vikunja.io/api >=0 <=2.2.0)

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