Temporal Server does not bind internal completion callbacks to the namespace that attaches them, allowing an authenticated user with write permission in one namespace to create a temporal://internal callback that targets a workflow in another namespace. The callback bypasses the component.callbacks.allowedAddresses allowlist and the History service delivers it to the referenced component regardless of the caller’s original namespace. When the forged callback matches an action that a target Scheduler V2 schedule is executing, the schedule is marked completed in the target namespace while its workflow continues, circumventing overlap policies such as SKIP, injecting attacker-controlled data into downstream workflows as a completion result, or pausing a schedule that is configured to pause on failure. The flaw requires knowledge of the target namespace identifier, schedule identifier, and timing of a running action, and it does not expose workflow payloads or history, but it permits cross‑namespace manipulation of schedule execution logic.

Temporal Technologies, Inc. – Temporal Server. Affected releases include all versions 1.30.0 and later up to, but not including, the fixes in releases 1.30.8, 1.31.4, and 1.32.1. Releases prior to 1.30.0 are not affected because the reserved internal callback address does not exist in those versions. Administrators who deploy or use Scheduler V2 must verify the exact minor‑release line and ensure it is upgraded to a fixed version.

The CVSS score of 6 indicates a moderate severity vulnerability. EPSS data is not available, and the vulnerability is not listed in CISA’s KEV catalog. Exploitation requires an authenticated user with write access in a source namespace, knowledge of the target namespace and schedule identifiers, and the timing of a running action. Those conditions limit the attack to privileged users, yet the impact can persist in any namespace that owns Scheduler V2 schedules, potentially allowing cross‑namespace state modification and unauthorized data flow.