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

Quick assessment

Affected
go-vikunja vikunja
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Vikunja 是一个开源的自托管任务管理平台。在版本 2.3.0 至 2.4.0 期间，拥有共享子项目“写入（Write）”权限但不具备“管理员（Admin）”权限的用户，可以通过向 提交 来将该子项目从其父级层级中分离出去。 中的 授权检查以及 中的 逻辑，仅对非零的父级 ID 值进行门控（即仅当 非零时才要求 Admin 权限），而 总是会将 持久化保存。因此，显式传入零值可以绕过为修复 CVE-2026-35595 而引入的 Admin 权限要求。 这种分离操作会切断递归的权限继承链，并可能干扰项目所有者的

CVSS 4.3 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
go-vikunja vikunja >= 2.3.0, < 2.4.0 affected
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I. Basic Information for CVE-2026-55064

Vulnerability Information
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Vulnerability Title
Vikunja incomplete fix for CVE-2026-35595: Write-only user can detach shared project from parent hierarchy via parent_project_id=0
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
go-vikunja vikunja >= 2.3.0, < 2.4.0 -

II. Public POCs for CVE-2026-55064

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III. Intelligence Information for CVE-2026-55064

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Patches & Fixes for CVE-2026-55064 (1)

Vendor Advisories for CVE-2026-55064 (1)

Vendor Pages for CVE-2026-55064 (1)

Same Patch Batch · go-vikunja · 2026-08-28 · 5 CVEs total

CVE-2026-55065 8.1 HIGH Vikunja: Improper Authorization and Authorization Bypass Through User-Controlled Key in co
CVE-2026-55066 7.1 HIGH Vikunja: Cross-tenant IDOR in kanban move-task endpoint via unauthorized body task_id
CVE-2026-54766 5.3 MEDIUM Vikunja: Project duplication bypasses write-permission check on the target parent project
CVE-2026-55067 5.0 MEDIUM Vikunja: Authenticated cross-tenant kanban-bucket relocation via `project_view_id` mass-as

IV. Related Vulnerabilities

Same product: vikunja
Same vendor: go-vikunja
Same weakness: CWE-862

V. Comments for CVE-2026-55064

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