CVE-2026-85580: SiYuan before v3.8.2 Path Guard Bypass via Case Mismatch
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
SiYuanto a version that resolves this vulnerability.Fixed in v3.8.2
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker needs low-privileged access to the SiYuan MCP file-access handler and network reachability to the affected service. No user interaction is required.
Which deployments are affected?
SiYuan versions before v3.8.2 are affected where the MCP file-access handler runs on a case-sensitive Linux filesystem. The issue results from case-sensitive path matching in the guard.
What information could be exposed?
An attacker can request a case-variant filename, such as PublishAccess.json, to read the protected publishAccess.json file. This can disclose sensitive publish-access configuration and metadata.
How can I determine whether exposure may have occurred?
Review requests handled by the MCP file-access endpoint for case variants of publishAccess.json, including PublishAccess.json. Successful responses containing publish-access configuration or metadata indicate exposure.