CVE-2026-33709
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedJupyterHub 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceJupyterHub prior to version 5.4.4 contains an open redirect vulnerability in its authentication flow. Attackers can craft malicious URLs that initially direct users to the JupyterHub login page, but after successful authentication, redirect them to an attacker-controlled external website, bypassing JupyterHub's built-in redirect validation checks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 5.4.4CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Determine installed JupyterHub versionRun 'jupyterhub --version' or check the package version via your package manager (e.g., pip show jupyterhub, conda list jupyterhub, or helm list for Kubernetes deployments)Affected if The version displayed is lower than 5.4.4 (e.g., 5.4.3, 5.4.0, 5.0.0, etc.)
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Verify JupyterHub is configured with authenticationCheck your jupyterhub_config.py file for auth-related settings (e.g., c.Authenticator.class, c.JupyterHub.authenticator_class) or inspect whether users are required to log inAffected if Authentication is enabled and users go through the login flow, which is the default configuration
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Identify login redirect configurationSearch your jupyterhub_config.py for 'redirect' or 'next' parameters (e.g., c.JupyterHub.default_url, any custom redirect_after_login settings)Affected if Any custom redirect URL configuration exists that could be exploited, or if using default settings without explicit allowlisting
Your environment is affected if JupyterHub version is below 5.4.4 and user authentication via the login flow is enabled.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped5.4.4
Upgrade JupyterHub to version 5.4.4 or later to patch the vulnerability. If immediate upgrade is not possible, implement URL allow-listing or network-level controls to restrict redirect destinations.
5.4.4 or later (latest stable release)
- 1. Identify current JupyterHub version by checking the running deployment or package management system
- 2. Upgrade JupyterHub to version 5.4.4 or later (preferably the latest stable release)
- 3. Restart the JupyterHub service to apply the update
- 4. Verify the upgrade was successful by checking the installed version matches or exceeds 5.4.4
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-33709 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-33709 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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