CVE-2026-114135

/// Technical description

Jupyter Server is the backend for Jupyter web applications. From 2.0.0 until 2.6.0, enabling GatewayClient.url replaced the normal KernelWebsocketHandler with WebSocketChannelsHandler, which authenticated the user but did not call authorizer.is_authorized(...) for the execute action on the kernels resource. A restricted authenticated user could therefore open an upstream kernel channel and obtain kernel execution despite the configured Authorizer denying that action, exposing data and credentials available to the kernel and permitting modification or disruption of the kernel environment. The default gateway configuration is fixed in version 2.6.0. In 2.6.0 and later, the same authorization bypass remains possible when a deployment manually registers the deprecated jupyter_server.gateway.handlers module, because its handler still omits the configured kernel-execute authorization decision.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References