CVE-2026-40934
MediumCVSS 6.8Exploitation Probability (EPSS)
Low risk23th percentile - higher than 23% of all known CVEs
Summary
Jupyter Server up to version 2.17.0 persists the secret used to sign authentication cookies to a static file and does not rotate it after a password change. After a password reset and server restart, previously issued cookies remain valid, allowing an attacker who captured a session cookie to retain access despite the password change.
Risk Assessment
The risk is that password changes do not invalidate existing sessions, potentially leading to persistent unauthorized access, especially in shared or public-facing environments.
Recommendation
Update Jupyter Server to version 2.18.0, which rotates the secret after a password change.
Original NVD description (English source)
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.