Jupyter Server's Authentication Cookies Remain Valid After Password Reset and Server Restart

Summary

A persistent cookie secret vulnerability allows authenticated users to maintain indefinite access even after password changes.

The cookie secret used to sign authentication cookies is stored in a permanent file (~/.local/share/jupyter/runtime/jupyter_cookie_secret) that is never automatically rotated or cleared, allowing stolen or compromised cookies to remain valid indefinitely regardless of password resets.

PoC

• Start a Jupyter server with password authentication: jupyter server password, jupyter server
• Log in with the password and capture the authentication cookie (e.g., just login with a browser).
• Change the password to revoke access: jupyter server password
• Restart the server
• Use the old stolen cookie => remains valid and provides full authenticated access.

Impact

• All jupyter-server deployments using password authentication where security incidents may occur
• Multi-user systems where one user's compromised session should be revocable by administrators
• Shared or public-facing Jupyter servers where credential rotation is a security requirement
• Any deployment where password changes are expected to revoke existing sessions

Patches

Jupyter Server 2.18+

Workaround

```bash

rm ~/.local/share/jupyter/runtime/jupyter_cookie_secret

Then restart the server

`