CVE-2026-40934 HIGH

CVE-2026-40934: jupyter-server authentication cookies remain valid after password reset due to static cookie secret

Vendor Jupyter-Server
Product jupyter_server
Weakness CWE-613 · Insufficient session expiration
Published May 5, 2026
Last update May 7, 2026

CVSS base score

7.6/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

May 5, 2026 CVE published
May 7, 2026 Record updated