CVE-2026-66394 PUBLISHED

SiYuan before v3.7.3 Stored and Reflected XSS via SVG Sanitizer Bypass

Assigner: VulnCheck
Reserved: 26.07.2026 Published: 27.07.2026 Updated: 28.07.2026

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:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
CVSS Score: 9.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	High
Attack Complexity	Low	Integrity	High	Integrity	High
Attack Requirements	None	Availability	None	Availability	None
Privileges Required	Low
User Interaction	Passive

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
CVSS Score: 8.7

Attack Vector	Network	Scope	Changed
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	Low	Integrity Impact	High
User Interaction	Required	Availability Impact	None

CVSS 3.1

Product Status

Vendor	siyuan-note
Product	siyuan
Versions	Default: unaffected affected from 0 to 3.7.3 (excl.) Version 3.7.3 is unaffected

Credits

JoyGhoshs reporter

References

Problem Types

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE