RCE in B3log Siyuan
CVE-2026-40322
SiYuan is an open-source personal knowledge management system. In versions 3.6.3 and below, Mermaid diagrams are rendered with securityLevel set to "loose", and the resulting SVG is injected into the DOM via innerHTML. This allows attacker-controlled javascript: URLs in Mermaid code blocks to survive into the rendered output. On desktop builds using Electron, windows are created with nodeIntegration enabled and contextIsolation disabled, escalating the stored XSS to arbitrary code execution when a victim opens a note containing a malicious Mermaid block and clicks the rendered diagram node. 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 9.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (42.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 42.2% 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: 0.005 · change: +0.002
Affected products
- B3log Siyuan
- Siyuan-Note Siyuan — versions < 3.6.4
Weakness classification (CWE)
References
- github.com/siyuan-note/siyuan/security/advisories/GHSA-x63q-3rcj-hhp5 (Third Party Advisory)
- github.com/siyuan-note/siyuan/releases/tag/v3.6.4 (Release Notes)
Frequently asked questions
- What is CVE-2026-40322?
- CVE-2026-40322 is a critical-severity vulnerability in B3log Siyuan, classified under Cross-site Scripting. CVSS score: 9.0/10. Published 2026-04-16.
- How severe is CVE-2026-40322?
- Critical severity. CVSS v3 base score is 9.0 out of 10.