CVE-2026-85580: Path Traversal (CVSS 6.5)

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.

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CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0053

Probability of exploitation

0.43%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-22 Path Traversal

References

Other 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

Frequently Asked Questions

What is CVE-2026-85580? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-85580? +

CVE-2026-85580 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0053, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-85580? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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