CVE-2026-114135 jupyter-server CVE debrief

Who should care

Defenders responsible for systems using Jupyter Server should assess exposure and prioritize verification and potential upgrades. This includes operators, platform administrators, vulnerability management teams, and security teams who need to understand the impact of this vulnerability on their systems and take appropriate actions to mitigate the risk.

Why it matters

Defenders should prioritize verifying exposure and assessing the impact of this vulnerability on their systems, particularly those using Jupyter Server, as it allows authenticated users to bypass kernel execute authorization.

• Authenticated users may bypass kernel execute authorization
• Potential for unauthorized kernel channel access
• Possible impact on system security and integrity

Technical summary

The gateway WebSocket handler in Jupyter Server 2.0.0 through 2.5.0 does not perform the expected authorization check before creating the WebSocket connection, allowing an authenticated user who is denied the `execute` action on the `kernels` resource to still open a kernel channel and send messages to the upstream kernel. This issue arises because the gateway handler only checks `current_user` and then opens the upstream channel without calling `authorizer.is_authorized(...)`. In contrast, the normal handler performs the expected authorization check before creating the WebSocket connection.

Defensive priority

Defenders should prioritize verifying exposure and assessing the impact of this vulnerability on their systems, particularly those using Jupyter Server.

Recommended defensive actions

• Verify the version of Jupyter Server being used and assess exposure
• Assess the impact of this vulnerability on systems using Jupyter Server
• Consider upgrading to Jupyter Server 2.6.0 or later
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is caused by the gateway WebSocket handler not performing the expected authorization check before creating the WebSocket connection. This handler checks that a user is authenticated but does not ask the configured Authorizer whether that user may execute kernels. The normal handler performs the expected authorization check before creating the WebSocket connection, but the gateway handler does not. This issue affects Jupyter Server 2.0.0 through 2.5.0. To verify exposure, defenders should review the version of Jupyter

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.