High severity · published Jul 27, 2026
CVE-2026-66394
SiYuan before v3.7.3 Stored and Reflected XSS via SVG Sanitizer Bypass
8.7
CVSS
0.3%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
High
Integrity
High
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 27% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SI
siyuan · siyuan-note
before 3.7.3 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-66394
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-66394
vendor-advisory
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-99rq-75j6-5j9f
third-party-advisory
https://www.vulncheck.com/advisories/siyuan-before-stored-and-reflected-xss-via-svg-sanitizer-bypass
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