Insufficient Session Expiration Affecting jupyter-server package, versions [,2.18.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published6 May 2026
- disclosed5 May 2026
- creditUnknown
Introduced: 5 May 2026
CVE-2026-40934 (opens in a new tab)How to fix?
Upgrade jupyter-server to version 2.18.0 or higher.
Overview
Affected versions of this package are vulnerable to Insufficient Session Expiration due to jupyter_cookie_secret never being automatically rotated or cleared. An attacker can keep or reuse authenticated session cookies after a password change by presenting a cookie signed with a secret that does not incorporate the current password. This lets the attacker retain access to the server as the affected user, exposing notebooks, files, and other authenticated server resources.
Workarounds
- Remove
~/.local/share/jupyter/runtime/jupyter_cookie_secretand restart the Jupyter server to invalidate existing authentication cookies, preventing stolen or old cookies from remaining valid after a password change.