CVE-2026-5724
MediumCVSS 6.3Exploitation Probability (EPSS)
Low risk41th percentile - higher than 41% of all known CVEs
Summary
The frontend gRPC server's streaming interceptor chain did not include the authorization interceptor. Configured ClaimMapper and Authorizer were bypassed for the AdminService/StreamWorkflowReplicationMessages endpoint, allowing unauthenticated access.
Risk Assessment
An attacker with network access to the frontend port can open the replication stream without authentication, potentially leading to data exfiltration if the cluster configuration is known and a valid replication target is configured.
Recommendation
Immediately upgrade Temporal Server to version 1.28.4, 1.29.6, 1.30.4, 1.31.2, or 1.32.0 (or later) depending on your release line.
Other vulnerabilities in Temporal Server
See all- CVE-2026-89139High
Temporal Server vulnerability allows an authenticated user with write access to a single namespace to execute arbitrary commands on the host running the Worker Service. The command is executed immediately, and since the Worker Service process holds credentials and TLS material for the entire cluster, the impact escalates to full cluster compromise. Affected versions are 1.31.0 through 1.31.2 (before 1.31.3), and the issue is present in default binaries and container images.
- CVE-2026-87858High
Temporal Server in releases 1.30.0 and later decided whether a Workflow completion callback was internal by reading a caller-supplied HTTP header. An authenticated caller with write permission in a single namespace could attach a callback whose 'source' header caused the request to be re-targeted at the internal frontend and executed as a system administrator against the administrative API. Releases 1.25.0 through 1.29.7 are affected by a narrower form of the same defect requiring the header to match a configured cluster ID.
- CVE-2026-16652High
Temporal Server did not bound the work performed while searching for a Schedule's next action time. An authenticated caller with namespace write permission could create or update a Schedule combining a fine-grained cadence with an exclusion calendar that rejects every candidate time, causing excessive CPU consumption in Frontend and Schedule worker components.
- CVE-2023-3485Low
Insecure defaults in open-source Temporal Server before version 1.20 on all platforms allow an attacker to craft a task token with access to a namespace other than the one specified in the request. This requires the namespace UUID and information from the workflow history for the target namespace.
Original NVD description (English source)
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. The fix was applied per release line: it is present in 1.28.4, 1.29.6, 1.30.4, 1.31.2, and 1.32.0 and later releases on each line. Releases 1.31.0 and 1.31.1 do not contain the fix and are affected. Temporal Cloud is not affected.