CVE-2026-34449: SiYuan: Cross-Origin RCE via Permissive CORS Policy and JavaScript Snippet Injection

Severity: critical (CVSS 9.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-03-31 · updated 2026-07-24
Weakness: CWE-942

Description

SiYuan is a personal knowledge management system. Prior to version 3.6.2, a malicious website can achieve Remote Code Execution (RCE) on any desktop running SiYuan by exploiting the permissive CORS policy (Access-Control-Allow-Origin: * + Access-Control-Allow-Private-Network: true) to inject a JavaScript snippet via the API. The injected snippet executes in Electron's Node.js context with full OS access the next time the user opens SiYuan's UI. No user interaction is required beyond visiting the malicious website while SiYuan is running. This issue has been patched in version 3.6.2.

Affected products

siyuan-note siyuan: before 3.6.2 — fixed in 3.6.2

How to fix

Upgrade to a fixed version: siyuan-note siyuan 3.6.2. Check the vendor advisory for mitigations.

References

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