CVE-2026-116167: SiYuan 2.9.0 before 3.8.7 XSS via check-auth to Parameter

Severity: medium (CVSS 6.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-10-25 · updated 2026-10-26
Weakness: CWE-79

Description

SiYuan from 2.9.0 before 3.8.7 contains a cross-site scripting vulnerability in the unauthenticated /check-auth page that assigns the to parameter to window.location.href without scheme validation. Attackers can send a crafted link with a javascript: URI that executes after victim login, invoking kernel APIs to read or modify workspace content and settings.

Affected products

siyuan-note siyuan: from 2.9.0 before 3.8.7 — fixed in 3.8.7

How to fix

Upgrade to a fixed version: siyuan-note siyuan 3.8.7. Check the vendor advisory for mitigations.

References

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-fmj3-xc2f-6w4w
https://www.vulncheck.com/advisories/siyuan-2.9.0-before-3.8.7-xss-via-check-auth-to-parameter

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