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Vulnerabilities

Vulnerability · CVE-2026-40934

Jupyter Server is the backend for Jupyter web applications.

Published May 5, 2026 · catalog updated Jul 25, 2026 · jupyter server

Check if you run it

No confirmed exploitation is on record for CVE-2026-40934. EPSS is 0.38%. Act only if a listed version of jupyter server is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.6
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.38%
Remediation
Version ranges on file
Affected products
cpe jupyter/jupyter server · stated jupyter server

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe jupyter/jupyter serverversion unspecified
  • stated jupyter server<= 2.17.0

How to fix CVE-2026-40934

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-40934. EPSS is 0.38%. Act only if a listed version of jupyter server is installed.

Which versions are affected?

Compare what you have installed with jupyter server <= 2.17.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-613: Insufficient Session Expiration. EPSS 0.38%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 5, 2026 · NIST NVD

    Detected

    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

  2. Jul 25, 2026 · NIST NVD

    Updated

    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

Sources

  • CVE.orgVulnerability recordCVE-2026-40934

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-40934

    30-day exploitation probability 0.4%

    first.org
  • NIST NVDVulnerability recordCVE-2026-40934

    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

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.