What is CVE-2026-27138?

CVE-2026-27138 is a medium-severity vulnerability in Golang Go, classified under Improper Certificate Validation. CVSS score: 5.9/10. Published 2026-03-06.

How severe is CVE-2026-27138?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Vulnerability in Golang Go

CVE-2026-27138

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.

Vulnerability class: Improper Certificate Validation

Published 2026-03-06 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.003 (22.6th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 23rd percentile — 22.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.003 · change: -0.000

Affected products

Golang Go — versions 1.26.0
Go Standard Library Crypto/x509 — versions 1.26.0-0

Weakness classification (CWE)

CWE-295 — Improper Certificate Validation

References

groups.google.com/g/golang-announce/c/EdhZqrQ98hk (Release Notes)
go.dev/issue/77953 (Issue Tracking)
go.dev/cl/752183 (Mailing List)
pkg.go.dev/vuln/GO-2026-4600 (Vendor Advisory)

Frequently asked questions

What is CVE-2026-27138?: CVE-2026-27138 is a medium-severity vulnerability in Golang Go, classified under Improper Certificate Validation. CVSS score: 5.9/10. Published 2026-03-06.
How severe is CVE-2026-27138?: Medium severity. CVSS v3 base score is 5.9 out of 10.