CVE-2026-33709: Jupyterhub JupyterHub Has An Open Redirect Vulnerability

MODERATE
Advisory Identifier: GHSA-3vff-hjqv-m7h8
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CVSS 6.1
CWE-601
Published
Advisory Summary

CVE-2026-33709 is a MODERATE (CVSS 6.1) jupyterhub has an open redirect vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Jupyterhub libraries in the PyPI ecosystem. The issue involves jupyterhub has an open redirect vulnerability. Remediation is available by upgrading affected packages to version 5.4.4.

CVE-2026-33709 at a Glance

CVE Identifier CVE-2026-33709
GHSA Identifier GHSA-3vff-hjqv-m7h8
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Jupyterhub
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-33709

To remediate this vulnerability, upgrade all affected Jupyterhub dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

jupyterhub fixed: 5.4.4 
pip install jupyterhub>=5.4.4
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show jupyterhub

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-33709, inspect your installed packages using pip:

pip show jupyterhub

Analyze the terminal output to locate any version of Jupyterhub in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.4.4), your application is affected.

Note: The pip show jupyterhub command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Jupyterhub, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## 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.

CVE-2026-33709 Affected Jupyterhub Versions

1 component(s)
Fixed Versions:
5.4.4
Product / Package Ecosystem Affected Versions Fixed Version
jupyterhub
pypi/jupyterhub
PyPI
< 5.4.4
5.4.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-3vff-hjqv-m7h8
NVD — CVE-2026-33709 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33709
Jupyterhub Source Repository REPOSITORY
https://github.com/jupyterhub/jupyterhub
Jupyterhub Release RELEASE
https://github.com/jupyterhub/jupyterhub/releases/tag/5.4.4

Frequently Asked Questions

What is CVE-2026-33709?
CVE-2026-33709 is a security vulnerability in Jupyterhub involving JupyterHub has an Open Redirect Vulnerability under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Jupyterhub versions are affected?
Affected versions include releases prior to 5.4.4 across affected packages: jupyterhub.
What version fixes CVE-2026-33709?
Upgrading to 5.4.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is jupyterhub affected?
Yes, jupyterhub is affected in releases prior to 5.4.4. Upgrade your dependency to 5.4.4 or later.
What is the CVSS score of CVE-2026-33709?
CVE-2026-33709 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-33709?
CVE-2026-33709 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check PyPI dependencies for CVE-2026-33709?
Run the dependency tree command: 'pip show jupyterhub'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3vff-hjqv-m7h8",
  "modified" : "2026-04-27T16:19:31Z",
  "published" : "2026-04-03T21:36:07Z",
  "aliases" : [ "CVE-2026-33709" ],
  "summary" : "JupyterHub has an Open Redirect Vulnerability",
  "details" : "## Affected Version\n\nJupyterHub <= 5.4.3\n\n## Impact\n\nAn 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.\n\n## Patches\n\nUpgrade to JupyterHub 5.4.4\n\n## Workarounds\n\nA deployment can apply filters on the Location header in a reverse proxy such as nginx/apache/traefik.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "jupyterhub"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.4.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.4.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-3vff-hjqv-m7h8"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33709"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jupyterhub/jupyterhub"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterhub/jupyterhub/releases/tag/5.4.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-601" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-03T21:36:07Z",
    "nvd_published_at" : "2026-04-03T22:16:26Z"
  }
}