CVE-2026-104355: CWE-863: Incorrect Authorization in Temporal Technologies, Inc. Temporal Server
Description
CVE-2026-104355 is a high-severity authorization vulnerability in Temporal Technologies, Inc.'s Temporal Server. In multi-cluster deployments, a connected peer cluster can modify local namespaces on another cluster without proper authorization. This occurs because the receiving cluster applies inbound namespace replication updates without verifying that the namespace is global or properly authorized. An attacker controlling a registered peer cluster can alter local namespace metadata, including critical namespaces like temporal-system, potentially disrupting workflow operations. Clusters without remote clusters registered with connection enabled are not affected.
CVSS v4.0
Score 7.0high
Affected software
Temporal Technologies, Inc.
Temporal Server
pkg:golang/go.temporal.io/servercpe:2.3:a:temporal:temporal:*:*:*:*:*:*:*:*Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability arises from incorrect authorization in Temporal Server's namespace replication logic. When a multi-cluster setup is used, the sending cluster excludes local namespaces from replication tasks, but the receiving cluster does not enforce the same restriction. It verifies only that namespace identifiers match and then overwrites namespace metadata such as state, description, owner, retention, archival settings, cluster list, and active cluster based on failover version. This allows a party controlling a registered peer cluster to modify any local namespace on the receiving cluster without credentials, including marking namespaces as Deprecated or changing retention policies, which can cause workflow failures. The issue affects namespace metadata refreshed during history replication tasks as well. Clusters without connected remote clusters are not exposed.
Potential Impact
An attacker who controls or compromises a registered peer cluster can modify local namespaces on the target Temporal Server cluster without authentication. This can lead to unauthorized changes in namespace metadata, including critical system namespaces, potentially causing workflow failures and operational disruption. The vulnerability affects multi-cluster deployments with connection enabled to remote clusters. Clusters without such configurations are not impacted.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict and monitor access to registered peer clusters and disable connection to remote clusters if not required to reduce exposure. There is no indication that this vulnerability is mitigated by default or that no action is required.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Temporal
- Date Reserved
- 2026-10-01T20:45:19.047Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6acd2f242cdf04f656c3e8b3
Added to database: 10/12/2026, 19:04:04 UTC
Last enriched: 10/12/2026, 19:19:04 UTC
Last updated: 10/12/2026, 19:19:04 UTC
Views: 9
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