# CVE-2026-104355: Temporal Server applies inbound namespace replication from a connected peer cluster to local namespaces

> CVE-2026-104355: Temporal Server applies inbound namespace replication from a connected peer cluster to local namespaces. CVSS 7.0 (CVSS 4.0).

Canonical: https://rewindex.com/cve/CVE-2026-104355
Last updated: 2026-10-16T19:55:59Z

- Published: 2026-10-12 18:43 UTC · Updated: 2026-10-16 19:55 UTC · Assigner: Temporal
- CVSS: 7.0 (CVSS 4.0) · Severity: High
- EPSS: 0.36%, 29th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-863

## Description

A connected peer cluster can modify a Temporal Server cluster's local namespaces, which are never replicated to that peer, because the receiving cluster applies inbound namespace replication updates to them. In a multi-cluster deployment, each cluster pulls replication tasks from the remote clusters an administrator has registered with connection enabled; the sending side excludes local namespaces, but the receiving side does not apply the same rule. When an inbound task names an existing namespace, the server checks at most that the namespace identifiers match, then overwrites its state, description, owner, retention, archival settings, and cluster list, and its active cluster when the task carries a higher failover version, without checking that the namespace is global. A party that controls a registered peer's replies, by operating or compromising it, can therefore change any local namespace whose name and identifier it can supply, without any credential on the receiving cluster: for example, marking it Deprecated, making the peer its active cluster, and shortening its retention, after which new Workflow starts in that namespace fail. Local namespaces include the built-in temporal-system namespace. Namespace metadata the History service refreshes from the peer while processing its history replication tasks passes through the same logic. A cluster with no remote cluster registered with connection enabled is not exposed.

## Affected vendors and products

- Temporal Technologies, Inc.: Temporal Server

## Tracked companies

- [Temporal Cloud](https://rewindex.com/company/temporal-cloud.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-104355)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-104355)
- [https://github.com/temporalio/temporal/blob/v1.0.0/common/namespace/replicationTaskExecutor.go\#L191-L260](https://github.com/temporalio/temporal/blob/v1.0.0/common/namespace/replicationTaskExecutor.go#L191-L260)
- [https://github.com/temporalio/temporal/commit/f2b571e2eee8a9143fbc4711f3db8b5a37146b3b](https://github.com/temporalio/temporal/commit/f2b571e2eee8a9143fbc4711f3db8b5a37146b3b)
- [https://github.com/temporalio/temporal/pull/12323](https://github.com/temporalio/temporal/pull/12323)
- [https://github.com/temporalio/temporal/pull/12328](https://github.com/temporalio/temporal/pull/12328)
- [https://github.com/temporalio/temporal/pull/12329](https://github.com/temporalio/temporal/pull/12329)
- [https://github.com/temporalio/temporal/pull/12330](https://github.com/temporalio/temporal/pull/12330)
- [https://github.com/temporalio/temporal/releases/tag/v1.30.8](https://github.com/temporalio/temporal/releases/tag/v1.30.8)
- [https://github.com/temporalio/temporal/releases/tag/v1.31.4](https://github.com/temporalio/temporal/releases/tag/v1.31.4)
- [https://github.com/temporalio/temporal/releases/tag/v1.32.1](https://github.com/temporalio/temporal/releases/tag/v1.32.1)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-104355 · Markdown: https://rewindex.com/cve/CVE-2026-104355.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-104355 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:14:54.448Z