Executive brief
Temporal Server is an open-source platform used to manage and execute complex business workflows. A security flaw in the system's batch processing allows a user with 'writer' permissions in one workspace (namespace) to potentially interfere with workflows in a different workspace on the same server. An attacker could delete, reset, or send signals to a victim's tasks if they know the specific workflow IDs, potentially disrupting business operations or causing data inconsistency.
Technical details
An authorization bypass (CWE-639) exists in Temporal Server's batch activity code. While the system validated the namespace ID, it failed to cross-check the user-provided namespace name against the worker's bound namespace. This allows a worker with privileged credentials in one namespace to operate on an arbitrary namespace if the server is configured with cross-namespace authorization (e.g., internal-frontend service or specific TLS-based internal identities). To exploit this, an attacker must have 'writer' role access and knowledge of the victim's specific workflow IDs and signal names. The issue was introduced in v1.29.0 and is patched in v1.29.5 and v1.30.3.
Affected products
- Temporal Technologies Temporal Server >= 1.29.0, < 1.29.5; >= 1.30.0, < 1.30.3
Timeline
- 2026-04-01: disclosed
- 2026-04-01: patched: Versions 1.29.5 and 1.30.3 released
- 2026-04-01: advisory