---
id: CVE-2026-85580
title: >-
  SiYuan versions before v3.8.2 contain a path guard bypass vulnerability in the
  MCP file-access handler that uses case-sensitive matching on Linux filesystems
summary: >-
  SiYuan versions before v3.8.2 contain a path guard bypass vulnerability in the
  MCP file-access handler that uses case-sensitive matching on Linux
  filesystems. Attackers can read the protected publishAccess.json file by
  requesting case-va…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-22
published: '2026-09-04'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T20:05:53.177'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-85580'
references:
  - url: >-
      https://github.com/siyuan-note/siyuan/security/advisories/GHSA-mmgw-3mx9-cfwp
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/siyuan-before-3.8.2-path-guard-bypass-via-case-mismatch
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/siyuan-note/siyuan/security/advisories/GHSA-mmgw-3mx9-cfwp
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00526
epssPercentile: 0.43525
ingestedAt: '2026-09-08T20:10:03.164Z'
---

## Overview

SiYuan versions before v3.8.2 contain a path guard bypass vulnerability in the MCP file-access handler that uses case-sensitive matching on Linux filesystems. Attackers can read the protected publishAccess.json file by requesting case-variant paths like PublishAccess.json to disclose sensitive publish-access configuration and metadata.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.