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Vulnerability record · CVE-2026-66394 · published 27 July 2026

CVE-2026-66394: Cross-site scripting vulnerability

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.

9.3 CVSS 4.0 Critical EPSS 0.47% · top 61.7% CWE-79 · Cross-site scripting Deferred
9.3CVSS 4.0 base score
0.47%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
28 Jul 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-99rq-75j6-5j9f
https://www.vulncheck.com/advisories/siyuan-before-stored-and-reflected-xss-via-svg-sanitizer-bypass
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-99rq-75j6-5j9f

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Source: NIST National Vulnerability Database (record CVE-2026-66394), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.