What’s Vulnerable › Vulnerabilities

CVE-2021-41247: incomplete logout in JupyterHub

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-11-04 · updated 2026-06-17
• Weakness: CWE-613

Description

JupyterHub is an open source multi-user server for Jupyter notebooks. In affected versions users who have multiple JupyterLab tabs open in the same browser session, may see incomplete logout from the single-user server, as fresh credentials (for the single-user server only, not the Hub) reinstated after logout, if another active JupyterLab session is open while the logout takes place. Upgrade to JupyterHub 1.5. For distributed deployments, it is jupyterhub in the _user_ environment that needs patching. There are no patches necessary in the Hub environment. The only workaround is to make sure that only one JupyterLab tab is open when you log out.

Affected products

• jupyterhub: from 1.0.0 before 1.5.0 — fixed in 1.5.0

How to fix

Upgrade to a fixed version: jupyterhub 1.5.0. Check the vendor advisory for mitigations.

References

• https://github.com/jupyterhub/jupyterhub/commit/5ac9e7f73a6e1020ffddc40321fc53336829fe27
• https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-cw7p-q79f-m2v7
• https://github.com/jupyterhub/jupyterhub/commit/5ac9e7f73a6e1020ffddc40321fc53336829fe27
• https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-cw7p-q79f-m2v7

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