CVE-2026-40322

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 v3.1 Score

9.0

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0005

Probability of exploitation

0.15%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

CWE-94 CWE-94

Affected Products

Vendor	Product	Versions
b3log	siyuan	< 3.6.4

References

Other References

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

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 9.0 (CRITICAL).

How severe is CVE-2026-40322? +

CVE-2026-40322 has a CVSS v3.1 score of 9.0 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0005, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-40322? +

CVE-2026-40322 affects products from b3log, specifically: siyuan. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-40322? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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