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CVE-2026-66394— SiYuan before v3.7.3 Stored and Reflected XSS via SVG Sanitizer Bypass

Quick assessment

Affected
siyuan-note siyuan
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

思源（SiYuan）在 v3.7.3 版本之前存在存储型及反射型跨站脚本（XSS）漏洞，该漏洞源于 SVG 净化机制的不完善。攻击者可通过绕过基于 HTML 解析器的清理程序，注入并执行恶意脚本。具体而言，攻击者可将 标签隐藏于 、 或 元素内部。HTML 解析器会将这些元素的内容视为纯文本，而当内容以 类型作为 SVG 图像提供时，浏览器会将其解析为可执行的 SVG 内容，从而导致在应用程序源上下文中执行脚本，造成跨站脚本攻击。

CVSS 8.7 · High EPSS 0.34% · P25

Affected Version Matrix 2

VendorProduct Version RangeStatus
siyuan-note siyuan < 3.7.3 affected
3.7.3 unaffected
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I. Basic Information for CVE-2026-66394

Vulnerability Information
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Vulnerability Title
SiYuan before v3.7.3 Stored and Reflected XSS via SVG Sanitizer Bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
siyuan-note siyuan 0 ~ 3.7.3 -

II. Public POCs for CVE-2026-66394

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Reproduction recording is a Pro+ exclusive
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claude_code · 7061 chars
GitHub 复现环境（可 clone 直接跑）
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III. Intelligence Information for CVE-2026-66394

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Vendor Advisories for CVE-2026-66394 (2)

Same Patch Batch · siyuan-note · 2026-07-27 · 3 CVEs total

CVE-2026-66395 9.6 CRITICAL SiYuan Desktop before v3.7.2 Reflected XSS to RCE via siyuan Protocol
CVE-2026-66396 8.4 HIGH SiYuan before v3.7.2 Stored XSS to RCE via title-img IAL

IV. Related Vulnerabilities

Same product: siyuan
Same vendor: siyuan-note
Same weakness: CWE-79

V. Comments for CVE-2026-66394

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