Bug 2558527 (CVE-2026-114135)

Summary: CVE-2026-114135 jupyter-server: jupyter-server: Unauthorized code execution via missing authorization check in gateway handler
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in jupyter-server. When configured with a gateway connection, the server validates user authentication but fails to verify whether the user has permission to run actions on computational kernels. A remote authenticated user with restricted privileges can exploit this flaw to open an unauthorized communication channel to an active kernel. This issue allows an attacker to execute arbitrary code, access sensitive credentials and data, or disrupt server environments.
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Description OSIDB Bzimport 2026-10-21 20:12:29 UTC 
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.