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CVE-2026-56765— Vikunja - Unauthenticated Instance-Wide Data Breach via Link Share Hash Disclosure Chained with Cross-Project Attachment IDOR

Quick assessment

Affected
Vikunja Vikunja
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Vikunja是Vikunja团队开源的一个待办事项应用程序。 Vikunja 2.2.1之前版本存在授权问题漏洞，该漏洞源于LinkSharing.ReadAll端点暴露共享哈希，且GetTaskAttachment端点按顺序ID获取附件时未验证所有权，可能导致授权权限提升至管理员级别。

CVSS 9.8 · Critical EPSS 0.51% · P42

Affected Version Matrix 2

VendorProduct Version RangeStatus
Vikunja Vikunja < 2.2.1 affected
2.2.1 unaffected
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I. Basic Information for CVE-2026-56765

Vulnerability Information
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Vulnerability Title
Vikunja - Unauthenticated Instance-Wide Data Breach via Link Share Hash Disclosure Chained with Cross-Project Attachment IDOR
Source: CVE Program / CVE List V5
Vulnerability Description
Vikunja before 2.2.1 contains an authorization flaw where the LinkSharing.ReadAll endpoint exposes share hashes to users with read access, enabling permission escalation to admin-level shares. The GetTaskAttachment endpoint performs permission checks against user-supplied task IDs but fetches attachments by sequential ID without verifying ownership, allowing attackers to download and delete all file attachments across all projects instance-wide.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5
Vulnerability Title
Vikunja 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Vikunja是Vikunja团队开源的一个待办事项应用程序。 Vikunja 2.2.1之前版本存在授权问题漏洞，该漏洞源于LinkSharing.ReadAll端点暴露共享哈希，且GetTaskAttachment端点按顺序ID获取附件时未验证所有权，可能导致授权权限提升至管理员级别。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Vikunja Vikunja 0 ~ 2.2.1 -

II. Public POCs for CVE-2026-56765

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 8498 chars
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III. Intelligence Information for CVE-2026-56765

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Vendor Advisories for CVE-2026-56765 (2)

IV. Related Vulnerabilities

Same product: Vikunja
Same weakness: CWE-639

V. Comments for CVE-2026-56765

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