XSS in Siyuan-Note Siyuan
CVE-2026-66394
SiYuan before v3.7.3 contains stored and reflected cross-site scripting vulnerabilities in SVG sanitization that allows authenticated attackers to execute scripts by bypassing the HTML parser-based cleaner. Attackers can hide script tags within desc, style, or noscript elements which the HTML parser treats as raw text but browsers interpret as executable SVG content when served as image/svg+xml, enabling script execution in the application origin.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.003 (18.7th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.7 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N.
Affected products
- Siyuan-note Siyuan — versions 0, 3.7.3
Weakness classification (CWE)
References
- disclosure@vulncheck.com (vendor-advisory)
- disclosure@vulncheck.com (third-party-advisory)
Frequently asked questions
- What is CVE-2026-66394?
- CVE-2026-66394 is a high-severity vulnerability in Siyuan-Note Siyuan, classified under Cross-site Scripting. CVSS score: 8.7/10. Published 2026-07-27.
- How severe is CVE-2026-66394?
- High severity. CVSS v3 base score is 8.7 out of 10.