CVE-2026-85580: SiYuan before v3.8.2 Path Guard Bypass via Case Mismatch

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-04 · updated 2026-09-08
Weakness: CWE-22

Description

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.

Affected products

siyuan-note siyuan: before 3.8.2 — fixed in 3.8.2

How to fix

Upgrade to a fixed version: siyuan-note siyuan 3.8.2. Check the vendor advisory for mitigations.

References

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-mmgw-3mx9-cfwp
https://www.vulncheck.com/advisories/siyuan-before-3.8.2-path-guard-bypass-via-case-mismatch
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-mmgw-3mx9-cfwp

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