CVE-2026-34605

Deeper analysis

SiYuan is a personal knowledge management system affected by an XSS vulnerability (CWE-79) in versions 3.6.0 through 3.6.1. The SanitizeSVG function added in 3.6.0 to protect the unauthenticated /api/icon/getDynamicIcon endpoint can be bypassed when an attacker supplies namespace-prefixed SVG elements such as <x:script xmlns:x="http://www.w3.org/2000/svg">. Because the Go HTML5 parser records the tag name literally as "x:script", the sanitization check passes the element through; the response is then served with Content-Type image/svg+xml and no Content-Security-Policy header, allowing a browser's XML parser to resolve the namespace and execute the script when the URL is loaded directly.

An unauthenticated remote attacker can exploit the flaw by crafting a malicious icon request that returns executable script in the SVG response. When a victim’s browser renders that response, the attacker can achieve arbitrary JavaScript execution in the victim’s context, resulting in high impact on confidentiality, integrity, and limited availability according to the CVSS 8.6 rating.

The project’s GitHub security advisory and release notes for version 3.6.2 state that the issue has been patched by updating the sanitization logic to handle namespace-prefixed elements correctly.

EPSS for the CVE rose from a low baseline of 0.0016 to a peak of 0.0107, indicating that exploitation interest increased after disclosure.