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Fencer Vulns
low 2.3

CVE-2026-5199 json

Cross Namespace Access via Batch Operation

published 2026-04-01 7 mo ago modified 2026-09-10 1 mo ago also GHSA-xpg8-3hhp-p7w8 , GO-2026-5766 , EUVD-2026-17995

cvss
2.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits
0
none known

Summary

A writer role user in an attacker-controlled namespace could signal, delete, and reset workflows or activities in a victim namespace on the same cluster. Exploitation requires the attacker to know or guess specific victim workflow ID(s) and, for signal operations, signal names. This was due to a bug introduced in Temporal Server v1.29.0 which inadvertently allowed an attacker to control the namespace name value instead of using the server's own trusted name value within the batch activity code. The batch activity validated the namespace ID but did not cross-check the namespace name against the worker's bound namespace, allowing the per-namespace worker's privileged credentials to operate on an arbitrary namespace. Exploitation requires a server configuration where internal components have cross-namespace authorization, such as deployment of the internal-frontend service or equivalent TLS-based authorization for internal identities.

This vulnerability also impacted Temporal Cloud when the attacker and victim namespaces were on the same cell, with the same preconditions as self-hosted clusters.

Patch / fix

  • go go.temporal.io/server 1.29.5, 1.30.3
  • Temporal Technologies, Inc. temporal 1.29.5, 1.30.3
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 2.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:L/SA:L/S:N/AU:Y/R:U/RE:M
CNA 4.0 2.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:L/SA:L/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:N/AU:Y/R:U/V:X/RE:M/U:X

Affected packages

ecosystem package affected fixed in
go go.temporal.io/server
>=1.30.0-143.0, <1.30.3
<1.29.5
1.30.3
1.29.5

Affected products

  • Temporal Technologies, Inc. temporal

Classification

Weakness
  • CWE-639 Authorization Bypass Through User-Controlled Key

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.