How severe is CVE-2026-33709?

No CVSS score has been assigned to CVE-2026-33709 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-33709?

CVE-2026-33709 affects the following packages: jupyterhub (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-33709?

Update jupyterhub to 5.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33709 is resolved across your whole dependency graph.

How do I detect CVE-2026-33709 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for jupyterhub, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-33709 if there is no patch (or I can't update yet)?

Stop reflecting attacker-controlled destinations: resolve every redirect target against an allowlist of paths or hosts you own, prefer a server-side key over a full URL in the request, and reject absolute URLs entirely where the flow only ever needs a relative one.

Is CVE-2026-33709 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-33709 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-33709?

CVE-2026-33709 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 12th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-33709?

CVE-2026-33709 is classified as Open Redirect (CWE-601). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-33709 published, and has it been updated?

CVE-2026-33709 was published on April 3, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-33709 — jupyterhub

CVE-2026-33709 is a Open Redirect vulnerability in jupyterhub. A fix is available for jupyterhub — see the affected versions and patch details below.

JupyterHub has an Open Redirect Vulnerability

Also known asBIT-jupyterhub-2026-33709GHSA-3vff-hjqv-m7h8PYSEC-2026-2188

Published

Apr 3, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33709.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs12th percentile — riskier than 12% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍jupyterhub

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Affected Version

JupyterHub <= 5.4.3

Impact

An open redirect vulnerability in JupyterHub <=5.4.3 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.

Patches

Upgrade to JupyterHub 5.4.4

Workarounds

A deployment can apply filters on the Location header in a reverse proxy such as nginx/apache/traefik.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`jupyterhub`	all versions	5.4.4`pip install --upgrade 'jupyterhub==5.4.4'`

Affected Products

1 product · 1 configurations

Application

jupyterhubjupyter

< 5.4.4

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for jupyterhub, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update jupyterhub to 5.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33709 is resolved across your whole dependency graph.
Workarounds
Stop reflecting attacker-controlled destinations: resolve every redirect target against an allowlist of paths or hosts you own, prefer a server-side key over a full URL in the request, and reject absolute URLs entirely where the flow only ever needs a relative one.

Frequently Asked Questions

## Affected Version JupyterHub <= 5.4.3 ## Impact An open redirect vulnerability in JupyterHub <=5.4.3 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. ## Patches Upgrade to JupyterHub 5.4.4 ## Workarounds A deployment can apply filters on the Location header in a reverse proxy such as nginx/apache/traefik.