CVE-2026-114135: Jupyter Server gateway WebSocket handler skips kernel authorization
Summary
CVE-2026-114135: Authenticated users denied kernel execution may still open kernel channels, execute code, and access data or credentials available to those kernels. Affects jupyter-server versions >= 2.0.0, < 2.6.0. Fixed in 2.6.0. How to fix ↓
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Background
Jupyter Server is a Python server package in the PyPI ecosystem. It provides the server-side services used by Jupyter applications, including kernel communication over WebSockets. Deployments can connect it to a Jupyter Gateway or Enterprise Gateway, where configured authorization rules control which authenticated users may execute kernels.
Vulnerability Detail
The missing authorization check lets an authenticated user bypass a restriction on kernel execution and send messages to an upstream kernel. In the default gateway configuration, Jupyter Server versions 2.0.0 through 2.5.0 replace the normal kernel channel handler with a gateway WebSocket handler that checks authentication but does not ask the configured Authorizer whether the user may execute kernels. This is an authorization bypass, not an authentication bypass, and can expose kernel-accessible data and credentials.
How To Fix
Latest published version: 2.21.1 as of 23 Oct 2026
pip install --upgrade "jupyter-server==2.21.1"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
2.6.0
This is the first release that contains the fix.
pip install --upgrade "jupyter-server==2.6.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
AI-generated workaround (not vendor-documented): For jupyter-server, disable gateway mode or restrict access to gateway WebSocket routes until upgrading. If gateway access is required, limit it to trusted users and verify that the configured authorization policy denies unauthorized kernel execution.
Documented mitigation:
authorizer.is_authorized(...)
Conclusion
Upgrade jupyter-server to 2.6.0 or later to address the default gateway configuration issue. The deprecated handler can still expose the behavior if registered directly, so review whether that handler is in use. Vulert monitors the dependencies in Pipfile.lock and alerts when a new vulnerability affects them; check an application at https://vulert.com/scanner.
See every vulnerability recorded for jupyter-server →
FAQ
CVE-2026-114135 affects jupyter-server 2.0.0 through 2.5.0 in the default gateway configuration.
CVE-2026-114135 can let an authenticated user open a kernel channel, execute code, and access data or credentials available to that kernel.
Upgrade jupyter-server to the minimum fixed version, 2.6.0.
For jupyter-server, disable gateway mode or restrict gateway WebSocket access to trusted users until upgrading.
Check Pipfile.lock manually for jupyter-server. Vulert can scan a manifest or SBOM and monitor the dependency at Vulert Scanner.
References
Related vulnerabilities
Recent vulnerabilities recorded for jupyter-server.
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