Jupyter Server: Gateway WebSocket handler bypasses kernel execute authorization

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.8 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-114135: 0.48% estimated exploitation activity in the next 30 days; percentile 41.76 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Jupyter Server's gateway WebSocket handler checks that a user is authenticated, but it does not ask the configured Authorizer whether that user may execute kernels. In Jupyter Server 2.0.0 through 2.5.0, enabling GatewayClient.url automatically replaced the normal kernel channel handler with this gateway-specific handler. An authenticated user who is denied the execute action on the kernels resource can therefore still open a kernel channel and send messages to the upstream kernel. Details The normal handler performs the expected authorization check before creating the WebSocket connection: https://github.com/jupyter-server/jupyterserver/blob/v2.5.0/jupyterserver/services/kernels/websocket.py#L39-L47 The gateway handler only checks currentuser and then opens the upstream channel. It never calls authorizer.isauthorized(...): https://github.com/jupyter-server/jupyterserver/blob/v2.5.0/jupyterserver/gateway/handlers.py#L49-L75…

Published by the source

22 Oct 2026, 15:46 UTC

Last modified by the source

22 Oct 2026, 16:00 UTC

Source last checked

26 Oct 2026, 13:55 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-354v-3q48-cv69

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-354v-3q48-cv69

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-354v-3q48-cv69

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# Patch Next advisory brief: CVE-2026-114135

Advisory: Jupyter Server: Gateway WebSocket handler bypasses kernel execute authorization
IDs: CVE-2026-114135, GHSA-354v-3q48-cv69
Record: https://patchnext.com/advisories/cve-2026-114135 (revision 3, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jupyter-server 2.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI jupyter-server: affected >= 2.0.0, < 2.6.0; fixed in 2.6.0

## Suggested inspection (read-only)
- `python -m pip show jupyter-server`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on jupyter-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-354v-3q48-cv69 (GitHub-reviewed advisory GHSA-354v-3q48-cv69 lists affected ranges: PyPI jupyter-server >=2.0.0 <2.6.0)
- Verified: https://osv.dev/vulnerability/GHSA-354v-3q48-cv69 (OSV record GHSA-354v-3q48-cv69 lists affected ranges: PyPI jupyter-server >=2.0.0 <2.6.0 (fixed))

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