CVE-2026-55064

Vikunja has an incomplete fix for CVE-2026-35595: Write-only user can detach shared project from parent hierarchy via parentprojectid=0

• Unauthorized hierarchy modification: A user with only Write permission can detach a child project from its parent, which should require Admin permission (as established by the CVE-2026-35595 fix for non-zero reparents).
• Permission inheritance disruption: The recursive CTE permission model traverses parent_project_id upward. Detaching a project severs this chain, potentially causing other collaborators who inherited access through the parent to lose their permissions on the detached project.
• Organizational disruption: The project moves from a structured hierarchy to a root-level project, breaking the owner's intended organizational structure.

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2026-55064 has a CVSS score of 4.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.0); upgrading removes the vulnerable code path.

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Use a pointer field *int64 for ParentProjectID to distinguish between "field omitted" (nil) and "explicitly set to 0" (detach). The fix commit itself acknowledges this at project.go:1017: "a proper fix needs a pointer field."

Alternatively, add a dedicated detach boolean field or a separate API endpoint for detaching projects, with its own Admin permission check.

1. What is CVE-2026-55064? CVE-2026-55064 is a medium-severity missing authorization vulnerability in code.vikunja.io/api (go), affecting versions >= 2.3.0, < 2.4.0. It is fixed in 2.4.0. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2026-55064? CVE-2026-55064 has a CVSS score of 4.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of code.vikunja.io/api are affected by CVE-2026-55064? code.vikunja.io/api (go) versions >= 2.3.0, < 2.4.0 is affected.
4. Is there a fix for CVE-2026-55064? Yes. CVE-2026-55064 is fixed in 2.4.0. Upgrade to this version or later.
5. Is CVE-2026-55064 exploitable, and should I be worried? Whether CVE-2026-55064 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-55064 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-55064? Upgrade code.vikunja.io/api to 2.4.0 or later.