CVE-2026-90769: Open Notebook server-side request forgery in /api/sources

Executive brief

Open Notebook is an open-source note-taking application. The application fails to validate URLs supplied to the /api/sources endpoint, allowing authenticated users to make arbitrary HTTP requests through the application server. An attacker with access can exploit this to read internal network services, cloud metadata, and localhost-bound services that should not be publicly accessible.

Technical details

This vulnerability is a server-side request forgery (SSRF) in the POST /api/sources endpoint. The application fails to properly validate or sanitize the URL parameter before making HTTP requests on behalf of the server. An authenticated user can supply arbitrary URLs pointing to internal services, cloud metadata endpoints (e.g., AWS EC2 instance metadata), or localhost services. The application will then perform the request directly, returning responses that may contain sensitive configuration, credentials, or internal data. Patches are available in version 1.11.0 and later.

Affected products

• lfnovo Open Notebook before 1.11.0

Timeline

• 2026-09-13: disclosed

References

• https://github.com/lfnovo/open-notebook
• https://github.com/lfnovo/open-notebook/blob/8889087e317177d7b6e286342ab34e0c9c01d43e/api/routers/sources.py