XSS in B3log Siyuan
CVE-2026-40922
SiYuan is an open-source personal knowledge management system. In versions 3.6.1 through 3.6.3, a prior fix for XSS in bazaar README rendering (incomplete fix for CVE-2026-33066) enabled the Lute HTML sanitizer, but the sanitizer does not block iframe tags, and its URL-prefix blocklist does not effectively filter srcdoc attributes which contain raw HTML rather than URLs. A malicious bazaar package author can include an iframe with a srcdoc attribute containing embedded scripts in their README. When other users view the package in SiYuan's marketplace UI, the payload executes in the Electron context with full application privileges, enabling arbitrary code execution on the user's machine. This issue has been fixed in version 3.6.4.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (29.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 29.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001
Affected products
- B3log Siyuan
- Siyuan-Note Siyuan — versions < 3.6.4
Weakness classification (CWE)
References
- github.com/siyuan-note/siyuan/security/advisories/GHSA-8q5w-mmxf-48jg (Exploit, Third Party Advisory)
- github.com/siyuan-note/siyuan/commit/b382f50e1880ed996364509de5a10a72d7409428 (Patch)
- github.com/advisories/GHSA-4663-4mpg-879v (Third Party Advisory)
- github.com/siyuan-note/siyuan/releases/tag/v3.6.4 (Release Notes)
Frequently asked questions
- What is CVE-2026-40922?
- CVE-2026-40922 is a medium-severity vulnerability in B3log Siyuan, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-04-17.
- How severe is CVE-2026-40922?
- Medium severity. CVSS v3 base score is 5.4 out of 10.