GHSA-68p4-j234-43mv

Summary

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.

Details

Vulnerable files:

• kernel/server/serve.go, lines 960-963 — CORS middleware
• kernel/api/snippet.go, lines 93-128 — snippet injection endpoint

Root cause: The CORS middleware unconditionally sets:

Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true
Access-Control-Allow-Private-Network: true

The Access-Control-Allow-Private-Network: true header explicitly opts into Chrome's Private Network Access specification, telling the browser that external websites are permitted to access this localhost service. Combined with Access-Control-Allow-Origin: *, any website on the internet can make authenticated cross-origin requests to the SiYuan API at 127.0.0.1:6806.

The auth middleware at kernel/model/session.go:251-280 checks the Origin header, but this check is bypassed because the browser sends the session cookie (set on 127.0.0.1) along with the cross-origin request, and the server validates the cookie before reaching the Origin check for unauthenticated sessions.

Attack chain:

1. User visits https://evil-attacker.com while SiYuan desktop is running
2. Malicious JS sends CORS preflight to http://127.0.0.1:6806 — SiYuan responds with permissive CORS headers
3. Browser sends actual POST to /api/snippet/setSnippet with the user's session cookie
4. SiYuan accepts the request and saves a malicious JS snippet
5. The snippet executes in Electron's renderer process with Node.js integration, achieving arbitrary code execution...