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

Source

https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-31807.yaml

Associated Vulnerability

Title: SiYuan has a SVG Sanitizer Bypass via `<animate>` Element — Unauthenticated XSS (CVE-2026-31807)
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.

Description

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.

File Snapshot

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