CVE-2026-104355

What it is

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.

At a glance

Exploitability

Can be exploited over the network with an admin-level account. High risk of data tampering.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-10-01 20:45 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-10-12 19:16 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-10-16 19:55 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 7.0 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-10-12 19:16 UTC

Last modified

2026-10-16 19:55 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-863 · Incorrect authorization

Record status

Awaiting Analysis

Attack profile CVSS 4.0 · 7.0

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

High

User interaction

None

Confidentiality

None

Integrity

High

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-104355.md and follow it. Check whether this project is affected by CVE-2026-104355. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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