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 ↗

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

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

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