CVE-2026-40934
Description
Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, the secret used to sign authentication cookies is persisted to a static file at ~/.local/share/jupyter/runtime/jupyter_cookie_secret and is never rotated when a user changes their password. After a password reset and server restart, any previously issued authentication cookie remains cryptographically valid because the signing key has not changed. An attacker who has captured a session cookie through any means retains full authenticated access to the server regardless of subsequent password changes. This affects deployments using password-based authentication, particularly shared or public-facing servers where credential rotation is expected to revoke existing sessions. This issue has been fixed in version 2.18.0.
How to fix
- jupyter jupyter_server2.18.0 or later
- jupyter-server2.18.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| jupyter jupyter_server | v < 2.18.0 | 2.18.0 |
| jupyter-serverPyPI | v < 2.18.0 | 2.18.0 |
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Attack Surface Management
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