What’s Vulnerable › Vulnerabilities
CVE-2026-40934: jupyter-server authentication cookies remain valid after password reset due to static cookie secret
- Severity: medium (CVSS 6.8 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.3% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2026-05-05 · updated 2026-07-25
- Weakness: CWE-613
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.
Affected products
- jupyter-server jupyter_server: before 2.18.0 — fixed in 2.18.0
How to fix
Upgrade to a fixed version: jupyter-server jupyter_server 2.18.0. Check the vendor advisory for mitigations.
References
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