PatchTheCVECVE-2026-40934: Jupyter Server is the backend for Jupyter web applications
CVE-2026-40934 is a medium-severity flaw (CVSS 6.8) affecting jupyter server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 attac
Why this priority
- Public exploit reference
A fixed release or distro patch exists.
Risk facts
| CVSS score | 6.8 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | Low |
| User interaction | None |
| EPSS exploit chance | 0.3% (top 74%) |
| CISA exploited list | No |
| Weakness | CWE-613 |
| Published | 2026-05-05 |
| Last modified | 2026-07-25 |
Last updated 2026-07-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-40934?
jupyter server: upgrade to 2.18.0. Exact commands for each OS are on this page.
Is CVE-2026-40934 being exploited?
CVE-2026-40934 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-40934 affect?
CVE-2026-40934 affects jupyter server. Severity is medium (CVSS 6.8). 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 ro
How urgent is CVE-2026-40934?
Priority 35/100. Public exploit reference
Software pages
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