XSS in B3log Siyuan
CVE-2026-34605
SiYuan is a personal knowledge management system. From version 3.6.0 to before version 3.6.2, the SanitizeSVG function introduced in version 3.6.0 to fix XSS in the unauthenticated /api/icon/getDynamicIcon endpoint can be bypassed by using namespace-prefixed element names such as <x:script xmlns:x="http://www.w3.org/2000/svg">. The Go HTML5 parser records the element's tag as "x:script" rather than "script", so the tag check passes it through. The SVG is served with Content-Type: image/svg+xml and no Content Security Policy; when a browser opens the response directly, its XML parser resolves the prefix to the SVG namespace and executes the embedded script. This issue has been patched in version 3.6.2.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.005 (38.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
Affected products
- B3log Siyuan
- Siyuan-note Siyuan — versions >= 3.6.0, < 3.6.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-34605?
- CVE-2026-34605 is a medium-severity vulnerability in B3log Siyuan, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-03-31.
- How severe is CVE-2026-34605?
- Medium severity. CVSS v3 base score is 6.1 out of 10.