Vulnerabilities in pkg:pypi/jupyterhub

PACKAGE
Advisory Identifier: GHSA-p43p-whwx-q52h
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Advisory Summary

CVE-2026-54338 is a MODERATE (CVSS 5.3) denial of service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Jupyterhub libraries in the PyPI ecosystem. The issue involves jupyterhub has unauthenticated denial of service via unbounded username logging on failed login. Remediation is available by upgrading affected packages to version 5.5.0.

8 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:pypi/jupyterhub

8 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:pypi/jupyterhub. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-p43p-whwx-q52h CVE-2026-54338 MODERATE JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login
GHSA-m68r-v472-jgq9 CVE-2026-40864 MODERATE JupyterHub has cross-origin form POSTs bypass XSRF (CWE-352)
GHSA-3vff-hjqv-m7h8 CVE-2026-33709 MODERATE JupyterHub has an Open Redirect Vulnerability
GHSA-9x4q-3gxw-849f CVE-2024-41942 HIGH JupyterHub has a privilege escalation vulnerability with the `admin:users` scope
GHSA-7xx3-qp5w-fw96 CVE-2020-36191 MODERATE Cross-Site Request Forgery in JupyterHub
GHSA-cw7p-q79f-m2v7 CVE-2021-41247 MODERATE incomplete JupyterHub logout with simultaneous JupyterLab sessions
GHSA-7r3h-4ph8-w38g CVE-2024-28233 HIGH Cross site scripting (XSS) in JupyterHub via Self-XSS leveraged by Cookie Tossing
GHSA-rv62-4pmj-xw6h CVE-2019-10255 MODERATE Open Redirect vulnerability in jupyterhub and notebook

CVE-2026-54338 at a Glance

CVE Identifier CVE-2026-54338
GHSA Identifier GHSA-p43p-whwx-q52h
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Jupyterhub
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 5.3

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:N/S:U/C:N/I:N/A:L).

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

How to Fix CVE-2026-54338

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: 5.5.0 
pip install jupyterhub>=5.5.0
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-2026-54338, 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 5.5.0), 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-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. 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

### Impact Invalid input to login resulted in unbounded logging output. Only form-based Authenticators (the default PAM Authenticator, but not the more widely used OAuthenticator) are affected. ### Patches Upgrade to 5.5.0. ### Workarounds Use an Authenticator that doesn't use a login form, such as OAuthenticator.

CVE-2026-54338 Affected Jupyterhub Versions

1 component(s)
Fixed Versions:
5.5.0
Product / Package Ecosystem Affected Versions Fixed Version
jupyterhub
pypi/jupyterhub
PyPI
< 5.5.0
5.5.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-p43p-whwx-q52h
NVD — CVE-2026-54338 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-54338
Security Fix Commit FIX COMMIT
https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a
Jupyterhub Source Repository REPOSITORY
https://github.com/jupyterhub/jupyterhub

Frequently Asked Questions

What is CVE-2026-54338?
CVE-2026-54338 is a security vulnerability in Jupyterhub involving JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login under CWE-400: Uncontrolled Resource Consumption.
Which Jupyterhub versions are affected?
Affected versions include releases prior to 5.5.0 across affected packages: jupyterhub.
What version fixes CVE-2026-54338?
Upgrading to 5.5.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is jupyterhub affected?
Yes, jupyterhub is affected in releases prior to 5.5.0. Upgrade your dependency to 5.5.0 or later.
What is the CVSS score of CVE-2026-54338?
CVE-2026-54338 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2026-54338?
CVE-2026-54338 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check PyPI dependencies for CVE-2026-54338?
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-p43p-whwx-q52h",
  "modified" : "2026-08-25T19:29:19Z",
  "published" : "2026-08-25T19:29:19Z",
  "aliases" : [ "CVE-2026-54338" ],
  "summary" : "JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login",
  "details" : "### Impact\n\nInvalid input to login resulted in unbounded logging output. Only form-based Authenticators (the default PAM Authenticator, but not the more widely used OAuthenticator) are affected.\n\n### Patches\n\nUpgrade to 5.5.0.\n\n### Workarounds\n\nUse an Authenticator that doesn't use a login form, such as OAuthenticator.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "jupyterhub"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.5.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-p43p-whwx-q52h"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-54338"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jupyterhub/jupyterhub"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-25T19:29:19Z",
    "nvd_published_at" : "2026-08-07T21:17:29Z"
  }
}