CVE-2026-27138

Panic in name constraint checking for malformed certificates in crypto/x509

CVE-2026-27138 is fixed in 5 products on 2 platforms, first by Go Programming Language 1.26.1, released March 5, 2026. It is not reported as exploited. Patch Radar priority: Routine.

RoutineFixed on 2 platforms

CVSS

5.9

Moderate

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0038

32nd percentile

Certificate verification can panic when a certificate in the chain has an empty DNS name and another certificate in the chain has excluded name constraints. This can crash programs that are either directly verifying X.509 certificate chains, or those that use TLS.

Where it's fixed

Product	Fixed in	Fix	Released
Windows apps
Go Programming Language	1.26.1	Go Programming Language 1.26.1	Mar 5, 2026
Linux
go1.26 · opensuse-leap 15.6	1.26.1-150000.1.6.1	SUSE-SU-2026:0876-1	Mar 11, 2026
go1.26 · opensuse-leap 16.0	1.26.1-160000.1.1	OPENSUSE-SU-2026:20342-1	Mar 11, 2026
go1.26 · sles 15.6	1.26.1-150000.1.6.1	SUSE-SU-2026:0876-1	Mar 11, 2026
go1.26 · sles 15.7	1.26.1-150000.1.6.1	SUSE-SU-2026:0876-1	Mar 11, 2026
go1.26-openssl · opensuse-leap 15.6	1.26.1-150600.13.3.1	SUSE-SU-2026:0976-1	Mar 23, 2026
go1.26-openssl · opensuse-leap 16.0	1.26.1-160000.1.1	OPENSUSE-SU-2026:20537-1	Apr 14, 2026
go1.26-openssl · sles 15.6	1.26.1-150600.13.3.1	SUSE-SU-2026:0976-1	Mar 23, 2026
go1.26-openssl · sles 15.7	1.26.1-150600.13.3.1	SUSE-SU-2026:0976-1	Mar 23, 2026
go1.26-openssl · sles 16.0	1.26.1-160000.1.1	SUSE-SU-2026:21195-1	Apr 14, 2026
golang-1.26 · Debian 14	1.26.1-1	DEBIAN-CVE-2026-27138	Mar 6, 2026
govulncheck-vulndb · opensuse-leap 15.6	0.0.20260317T205859-150000.1.152.1	SUSE-SU-2026:1042-1	Mar 25, 2026
govulncheck-vulndb · opensuse-leap 16.0	0.0.20260723T184607-160000.1.1	OPENSUSE-SU-2026:21483-1	Jul 30, 2026

Details

Published
March 6, 2026
Weakness
CWE-1285: Improper Validation of Specified Index, Position, or Offset in Input
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-27138

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