# CVE-2026-55064: Vikunja has an incomplete fix for CVE-2026-35595: Write-only user can detach shared project from parent hierarchy via parent_project_id=0

> A write-only user can detach a shared project from its parent hierarchy, bypassing admin checks and disrupting permission inheritance.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Aug 2026
- **Updated:** 28 Aug 2026
- **Also known as:** GHSA-44v6-7fxq-vgf4, GO-2026-6306

## What is CVE-2026-55064?

CVE-2026-55064 is a medium-severity missing authorization vulnerability in go-vikunja vikunja, published on 28 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Vikunja is an open-source self-hosted task management platform. From 2.3.0 until 2.4.0, a user with Write but not Admin permission on a shared child project can detach it from its parent hierarchy by submitting parent_project_id equal to 0 to POST /api/v1/projects/{project}. The Project.CanUpdate authorization check in pkg/models/project_permissions.go and UpdateProject logic in pkg/models/project.go only gate nonzero parent values, while UpdateProject always persists parent_project_id, so the explicit zero value bypasses the Admin requirement introduced for CVE-2026-35595. Detachment severs the recursive permission-inheritance chain and can disrupt the owner’s hierarchy and inherited collaborator access. This issue is fixed in version 2.4.0.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-55064?

3 open source packages ship an affected version, including code.vikunja.io/api.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `code.vikunja.io/api` | Go | All versions | None |
| `code.vikunja.io/api` | Go | From 2.3.0 | 2.4.0 |
| `code.vikunja.io/api` | Go | From 2.3.0 | 2.4.0 |

## How do I fix CVE-2026-55064?

Upgrade code.vikunja.io/api to 2.4.0 or later.

## Is CVE-2026-55064 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55064 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55064 and fix it if it is affected.

What it is: CVE-2026-55064 is a medium-severity missing authorization vulnerability in go-vikunja vikunja, published on 28 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55064 exists.

Affected packages and fixed versions:
- code.vikunja.io/api (Go): affected all versions; no fix listed
- code.vikunja.io/api (Go): affected from 2.3.0; fixed in 2.4.0
- code.vikunja.io/api (Go): affected from 2.3.0; fixed in 2.4.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55064/ (Markdown: https://insights.sbomify.com/CVE-2026-55064/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55064
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55064
- OSV: https://osv.dev/vulnerability/CVE-2026-55064

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55064/
Summaries are generated and may contain mistakes; the official description above is the record.