The frontend gRPC server's streaming interceptor chain did not include the authorization interceptor. When a ClaimMapper and Authorizer are configured, unary RPCs enforce authentication and authorization, but the streaming AdminService/StreamWorkflowReplicationMessages endpoint accepted requests without credentials. This endpoint is registered on the same port as WorkflowService and cannot be disabled independently. An attacker with network access to the frontend port could open the replication stream without authentication. Data exfiltration is possible, but only when a configured replication target is correctly configured and the attacker has knowledge of the cluster configuration, as the history service validates cluster IDs and peer membership before returning replication data.

Executables from Temporal Technologies, Inc. marked as temporal are impacted. Any deployment of Temporal that includes a replication target and uses the default streaming replication endpoint is vulnerable until an update is applied. The patch versions listed in the advisory – specifically v1.28.4, v1.29.6, v1.30.4, v1.31.2, and any release 1.32.0 or newer – have addressed the issue, but releases 1.31.0 and 1.31.1 remain affected.

Vulnerability involves an unauthorized replication stream endpoint that bypasses authentication. The CVSS score of 6.3 indicates moderate severity. EPSS indicates a very low exploitation probability, and the vulnerability is not listed in the CISA KEV catalog, suggesting it is not actively exploited at scale. Based on the description, the likely attack vector is a malicious actor who can reach the Temporal frontend gRPC port, which is often exposed to internal or compromised networks. Exploitation also mandates knowledge of the replication target; therefore, risk is higher in environments where replication is enabled and not properly isolated. Temporal Cloud deployments are not affected.