CVE-2026-27137 Incorrect enforcement of email constraints in crypto/x509

What is CVE-2026-27137?

CVE-2026-27137 is a high-severity vulnerability in Golang Go, published on 6 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

When verifying a certificate chain which contains a certificate containing multiple email address constraints which share common local portions but different domain portions, these constraints will not be properly applied, and only the last constraint will be considered.

Weakness: CWE-295

Which versions are affected by CVE-2026-27137?

2 open source packages ship an affected version, including golang and stdlib. It affects 1 product.

Products include Golang Go.

How do I fix CVE-2026-27137?

Upgrade golang to 1.26.1 or later.

Is CVE-2026-27137 being exploited?

There is no known exploitation of CVE-2026-27137 in the wild and no public exploit code.

Other vulnerabilities in Golang Go

• CVE-2020-0601 Microsoft Windows CryptoAPI Spoofing Exploited High 8.1
• CVE-2026-27143 Missing bound checks can lead to memory corruption in safe Go in cmd/compile Critical 9.8
• CVE-2024-24790 Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip Critical 9.8
• CVE-2023-39320 Arbitrary code execution via go.mod toolchain directive in cmd/go Critical 9.8
• CVE-2023-24540 Improper handling of JavaScript whitespace in html/template Critical 9.8

All Golang Go vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-79613, AZL-79628, BELL-CVE-2026-27137, BIT-golang-2026-27137, CLEANSTART-2026-CO42319, CLEANSTART-2026-EL50504 and 297 more.