CVE-2026-40934 Details
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.
A vulnerability in Jupyter Server in versions through 2.17.0 allows authentication cookies to remain valid indefinitely, even after a password reset. The secret used to sign these cookies is stored in a static file and is not rotated when a user changes their password. As a result, an attacker who captures a session cookie can maintain full authenticated access to the server, regardless of subsequent password changes. This issue primarily affects deployments using password-based authentication, especially on shared or public-facing servers where credential rotation is expected to revoke existing sessions.
Users can upgrade to Jupyter Server version 2.18.0 or later, or manually remove the cookie secret file and restart the server.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 7, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-5mrq-x3x5-8v8f | [email protected] | ExploitMitigationVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-613 | Insufficient Session Expiration | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| jupyter jupyter server | < 2.18.0 |
CPE
Remediation
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Change History
7 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 25, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Jun 17, 2026 | CVE Modified | [email protected] |
| May 11, 2026 | Initial Analysis | [email protected] |
| May 7, 2026 | CVE Modified | CISA-ADP |
| May 6, 2026 | CVE Modified | CISA-ADP |
| May 5, 2026 | New CVE Received | [email protected] |