CVE-2026-40322Public exploitNetwork attack vector

User-assisted RCE via unsafe Mermaid SVG injection

Published Apr 16, 2026 · Updated Apr 16, 2026

Stored XSS in SiYuan 3.6.3 and earlier allows remote authenticated users to execute OS commands through malicious Mermaid notes. mermaidRender uses loose Mermaid security, preserves javascript URLs, and inserts the generated SVG through innerHTML into a Node-enabled Electron renderer. Execution requires a victim to open the attacker-controlled note and click its rendered diagram node; browser deployments remain limited to stored XSS.

CVSS severity9.0
Critical
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in SiYuan 3.6.3 and earlier allows remote authenticated users to execute OS commands through malicious Mermaid notes. mermaidRender uses loose Mermaid security, preserves javascript URLs, and inserts the generated SVG through innerHTML into a Node-enabled Electron renderer. Execution requires a victim to open the attacker-controlled note and click its rendered diagram node; browser deployments remain limited to stored XSS.

The record

CVE
CVE-2026-40322
Published
Apr 16, 2026
Updated
Apr 16, 2026
Vendor
SiYuan Note
Product
SiYuan
Classifications
CWE-79, CWE-94, T1203, T1204.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.6.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

SiYuan Note · SiYuanversion=< 3.6.4

Published CVSS scores

9.0GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-94Improper Control of Generation of Code ('Code Injection')
T1203Exploitation for Client Execution
T1204.001Malicious Link

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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