CVE-2026-66394 | SiYuan before v3.7.3 contains stored and reflected cross-sit… | CVSS 8.7 HIGH

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.

Metadata

CVE ID: CVE-2026-66394
State: PUBLISHED
Assigner: VulnCheck
Reserved: 2026-07-26 12:22 UTC
Published: 2026-07-27 15:43 UTC
Last updated: 2026-07-28 01:06 UTC
Primary CWE: CWE-79
Improper Neutralization of Input During Web Page Generation …
Vendor / Product: siyuan-note / siyuan
Sources: cve.org · NVD

Severity & Metrics

8.7 HIGH CVSS 3.1

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

SSVC — CISA Coordinator

Exploitation: PoC
Automatable: no
Tech. Impact: partial

Affected products (1)

Vendor	Product	Platform	Versions
siyuan-note	siyuan	—	0 < 3.7.3, 3.7.3

Weakness (CWE)

CWE	Source	Description
CWE-79	cna	Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS scores (2)

Score	Severity	Version	Source	Vector
9.3	CRITICAL	4.0	cna	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
8.7	HIGH	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

References (2)

GitHub Security Advisory (GHSA-99rq-75j6-5j9f) https://github.com/siyuan-note/siyuan/security/advisories/GHSA-99rq-75j6-5j9f
VulnCheck Advisory: SiYuan before v3.7.3 Stored and Reflected XSS via SVG Sanitizer Bypass https://www.vulncheck.com/advisories/siyuan-before-stored-and-reflected-xss-via-svg-sanitizer-bypass