EUVD-2026-290477

fkie_cve-2026-35595

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, the CanUpdate check at pkg/models/project_permissions.go:139-148 only requires CanWrite on the new parent project when changing parent_project_id. However, Vikunja's permission model uses a recursive CTE that walks up the project hierarchy to compute permissions. Moving a project under a different parent changes the permission inheritance chain. When a user has inherited Write access (from a parent project share) and reparents the child project under their own project tree, the CTE resolves their ownership of the new parent as Admin (permission level 2) on the moved project. This vulnerability is fixed in 2.3.0.

GHSA-2vq4-854f-5c72 — Vikunja vulnerable to Privilege Escalation via Project Reparenting

Affected: Go: code.vikunja.io/api

## Summary

A user with Write-level access to a project can escalate their permissions to Admin by moving the project under a project they own. After reparenting, the recursive permission CTE resolves ownership of the new parent as Admin on the moved project. The attacker can then delete the project, manage shares, and remove other users' access.

## Details

The `CanUpdate` check at `pkg/models/project_permissions.go:139-148` only requires `CanWrite` on the new parent project when changing `parent_project_id`. However, Vikunja's permission model uses a recursive CTE that walks up the project hierarchy to compute permissions. Moving a project under a different parent changes the permission inheritance chain.

When a user has inherited Write access (from a parent project share) and reparents the child project under their own project tree, the CTE resolves their ownership of the new parent as Admin (permission level 2) on the moved project.

```go if p.ParentProjectID != 0 && p.ParentProjectID != ol.ParentProjectID { newProject := &Project{ID: p.ParentProjectID} can, err := newProject.CanWrite(s, a) // Only checks Write, not Admin if err != nil { return false, err } if !can { return false, ErrGenericForbidden{} } } ```

## Proof of Concept

Tested on Vikunja v2.2.2.

``` 1. victim creates "Parent Project" (id=3) 2. victim creates "Secret Child" (id=4) under Parent Project 3. victim shares Parent Project with attacker at Write level (per…

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EUVD-2026-290477

fkie_cve-2026-35595

GHSA-2vq4-854f-5c72 — Vikunja vulnerable to Privilege Escalation via Project Reparenting