CVE-2026-40322
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.31%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 9.0 CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
- EPSS
- 0.31% probability · 23th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-79, CWE-94
- Affected
- b3log/siyuan
- Source
- security-advisories@github.com
References
- https://github.com/siyuan-note/siyuan/releases/tag/v3.6.4Release Notes
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-x63q-3rcj-hhp5Third Party Advisory
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-x63q-3rcj-hhp5Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.