CVE-2026-27138 Panic in name constraint checking for malformed certificates in crypto/x509
A panic in Go's crypto/x509 package allows attackers to crash applications verifying TLS or X.509 certificates via malformed name constraints.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-27138?
CVE-2026-27138 is a medium-severity denial of service 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
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.
Weakness: CWE-295
Which versions are affected by CVE-2026-27138?
2 open source packages ship an affected version, including golang and stdlib. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
golang Bitnami | From 1.26.0-0 | 1.26.1 |
stdlib Go | From 1.26.0-0 | 1.26.1 |
Products include Golang Go.
How do I fix CVE-2026-27138?
Upgrade golang to 1.26.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-27138 being exploited?
There is no known exploitation of CVE-2026-27138 in the wild and no public exploit code.
Other vulnerabilities in Golang Go
- CVE-2020-0601 Microsoft Windows CryptoAPI Spoofing
- CVE-2026-27143 Missing bound checks can lead to memory corruption in safe Go in cmd/compile
- CVE-2024-24790 Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip
- CVE-2023-39320 Arbitrary code execution via go.mod toolchain directive in cmd/go
- CVE-2023-24540 Improper handling of JavaScript whitespace in html/template
Sources
Also known as AZL-79610, AZL-79625, BELL-CVE-2026-27138, BIT-golang-2026-27138, CLEANSTART-2026-DK85212, CLEANSTART-2026-NA69133 and 295 more.