What is CVE-2026-66395?

CVE-2026-66395 is a critical-severity vulnerability in Siyuan-Note Siyuan, classified under Cross-site Scripting. CVSS score: 9.6/10. Published 2026-07-27.

How severe is CVE-2026-66395?

Critical severity. CVSS v3 base score is 9.6 out of 10.

XSS in Siyuan-Note Siyuan

CVE-2026-66395

SiYuan desktop before v3.7.2 contains a reflected cross-site scripting vulnerability in the bazaar plugin readme handler that allows attackers to execute arbitrary code by crafting a malicious siyuan:// deep link. Attackers can inject HTML payloads via the plugin name parameter that execute with full Node.js access through insertAdjacentHTML rendering in an insecurely configured Electron renderer.

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.003 (25.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.6 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.

Affected products

Siyuan-note Siyuan — versions 0, 3.7.2

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

disclosure@vulncheck.com (vendor-advisory)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-66395?: CVE-2026-66395 is a critical-severity vulnerability in Siyuan-Note Siyuan, classified under Cross-site Scripting. CVSS score: 9.6/10. Published 2026-07-27.
How severe is CVE-2026-66395?: Critical severity. CVSS v3 base score is 9.6 out of 10.