XSS in B3log Siyuan
CVE-2026-31807
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.005 (40.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 40.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.001
Affected products
- B3log Siyuan
- Siyuan-Note Siyuan — versions < 3.5.10
Weakness classification (CWE)
References
- github.com/siyuan-note/siyuan/security/advisories/GHSA-5hc8-qmg8-pw27 (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-31807?
- CVE-2026-31807 is a medium-severity vulnerability in B3log Siyuan, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-03-10.
- How severe is CVE-2026-31807?
- Medium severity. CVSS v3 base score is 6.1 out of 10.