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CVE-2026-40322

SiYuan: Mermaid `javascript:` Link Injection Leads to Stored XSS and Electron RCE

Published: Apr 16, 2026Updated: Apr 20, 2026 Sources: CVE List NVDCWE-79
NVD MITRE
9.0CVSSCRITICAL
EPSS Score
0.3%
Top 78.0%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available

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 Vector Breakdown

AV:NAC:LPR:LUI:RS:CC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:RUser Interaction
Required
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-79CWE-94

Affected Products

siyuanb3log
On-premWeb App
Web & CMS Plugins / cms-core
siyuansiyuan-note
b3logoss-projectWeb & CMS Pluginsaka b3log

Attack Graph

Products CVE Techniques Tactics

Click technique nodes to view MITRE ATT&CK details. Scroll to zoom, drag to pan.

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

MITRE ATT&CK

3 techniques
Execution
Initial Access
View detailed technique mapping

References

https://github.com/siyuan-note/siyuan/releases/tag/v3.6.4
github.com
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-x63q-3rcj-hhp5
github.com

Timeline

Published
Apr 16, 2026
Last Updated
Apr 20, 2026

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