Insufficient Namespace Binding in Temporal Server Workflow History

CVE-2026-87857

What is CVE-2026-87857?

A vulnerability in the Temporal Server arises from inadequate binding of pagination tokens to the corresponding namespace and workflow during history retrieval requests. The design flaw allows an authenticated user, who has read permissions on one namespace, to access workflow history from another namespace, provided the workflow identifies the same History shard. This situation occurs because the pagination token lacks namespace and workflow identity, leading to potential unauthorized access to sensitive workflow data. The affected versions of the Temporal Server did not include checks to prevent this unauthorized access, and detection mechanisms for the issue were limited. Fixes have been implemented in newer releases to ensure proper binding and logging of pagination tokens.

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