---
title: "CVE-2026-104355: Temporal Server - Broken Access Control"
description: "Temporal Server in multi-cluster deployments contains a broken access control vulnerability caused by improper validation of inbound namespace replication updates, letting a connected peer cluster modify local namespaces without credentials, exploit requires control over a registered peer cluster."
url: https://panop.io/threat-heartbeat/CVE-2026-104355/
---

# CVE-2026-104355 Temporal Server - Broken Access Control

Temporal Server in multi-cluster deployments contains a broken access control vulnerability caused by improper validation of inbound namespace replication updates, letting a connected peer cluster modify local namespaces without credentials, exploit requires control over a registered peer cluster.

CVSS base score 7.0 /10

High

CISA KEV

Not listed

Public exploit

None known

EPSS

0.36% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-104355)

## Details

Type

Broken Access Control

Impact

Denial Of Service, Broken Access Control

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Published

12 October 2026

Updated

15 October 2026

Weakness

[CWE-863](https://cwe.mitre.org/data/definitions/863.html)

## Vendor fix

Update to the latest Temporal Server version with fixed namespace replication validation.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-104355](https://nvd.nist.gov/vuln/detail/CVE-2026-104355)
- [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)
- [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)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

Panop answers these inside your environment, for this CVE and every other finding.

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