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CVE-2026-31807— SiYuan has a SVG Sanitizer Bypass via `<animate>` Element — Unauthenticated XSS

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.

SiYuan是SiYuan开源的一个隐私至上的个人知识管理系统。 SiYuan 3.5.10之前版本存在跨站脚本漏洞，该漏洞源于SVG清理器未阻止SVG动画元素，可能绕过静态清理并导致反射型跨站脚本攻击。

AI Predicted 8.1 Difficulty: Moderate EPSS 0.45% · P37

Public Exploits 1

Nuclei · 1 CVE-2026-31807.yaml [template]
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I. Basic Information for CVE-2026-31807

Vulnerability Information
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Vulnerability Title
SiYuan has a SVG Sanitizer Bypass via `<animate>` Element — Unauthenticated XSS
Source: CVE Program / CVE List V5
Vulnerability Description
SiYuan is a personal knowledge management system. Prior to 3.5.10, SiYuan's SVG sanitizer (SanitizeSVG) blocks dangerous elements (<script>, <iframe>, <foreignobject>) and removes on* event handlers and javascript: in href attributes. However, it does NOT block SVG animation elements (<animate>, <set>) which can dynamically set attributes to dangerous values at runtime, bypassing the static sanitization. This allows an attacker to inject executable JavaScript into the unauthenticated /api/icon/getDynamicIcon endpoint (type=8), creating a reflected XSS. This is a bypass of the fix for CVE-2026-29183 (fixed in v3.5.9). This vulnerability is fixed in v3.5.10.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA: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
Vulnerability Title
SiYuan 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SiYuan是SiYuan开源的一个隐私至上的个人知识管理系统。 SiYuan 3.5.10之前版本存在跨站脚本漏洞，该漏洞源于SVG清理器未阻止SVG动画元素，可能绕过静态清理并导致反射型跨站脚本攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
siyuan-note siyuan < 3.5.10 -

II. Public POCs for CVE-2026-31807

# POC Description Source Link Shenlong Link
1 SiYuan <= v3.5.9 contains a reflected XSS caused by insufficient SVG sanitization allowing SVG animation elements to inject executable JavaScript in /api/icon/getDynamicIcon endpoint, letting unauthenticated attackers execute scripts. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-31807.yaml POC Details
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III. Intelligence Information for CVE-2026-31807

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Vendor Advisories for CVE-2026-31807 (1)

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-31807

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