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CVE-2026-54069 – Authentication Bypass – SiYuan Note ≤ 3.6.5

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Summary

CVE-2026-54069 is an authentication bypass vulnerability affecting SiYuan Note versions 3.6.5 and earlier, a self-hosted, open-source personal knowledge management system. The flaw stems from the application’s CheckAuth middleware unconditionally trusting any HTTP request that presents a chrome-extension:// Origin header, granting full administrator access without validating the configured access token. Unauthenticated remote attackers can exploit this against any internet-exposed SiYuan instance to gain unrestricted access to all stored notes, files, and administrative API endpoints.

Technical details

  • Root cause: The CheckAuth middleware contains an Origin Validation Error (CWE-346): it unconditionally grants RoleAdministrator privileges to any request carrying a chrome-extension:// Origin header, bypassing the configured access token check entirely.
  • Trigger conditions: An attacker sends a crafted HTTP POST request (e.g., to /api/system/getConf) with the header Origin: chrome-extension://<any-value>. No credentials, session token, or prior authentication are required.
  • Attack vector: Remote, unauthenticated, over HTTP/HTTPS. No user interaction is required.
  • Impact: Successful exploitation grants full administrator-level access to the SiYuan API. An attacker can read all workspace notes and files, retrieve the API access token from the system configuration, and invoke all administrative endpoints including plugin installation and system management functions.

Affected software

  • SiYuan Note ≤ 3.6.5

Severity

  • CVSS v3.1 Base Score: 9.1 (as reported in the ProjectDiscovery nuclei detection template; no official NVD entry or CVSS vector string has been published at the time of writing)

Mitigation and recommended actions

  • Immediate: Upgrade to SiYuan Note v3.7.0 or later, which resolves the Origin validation flaw in the CheckAuth middleware.
  • If patching is not immediately possible:
    • Restrict network access to the SiYuan web server (default port 6806) to trusted IP addresses only, using firewall rules or reverse proxy access controls.
    • Do not expose SiYuan directly to the public internet until the patch has been applied.
    • Consider temporarily disabling external access or placing the instance behind a VPN gateway.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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