CVE-2026-33810 Case-sensitive excludedSubtrees name constraints cause Auth Bypass in crypto/x509
Attackers can bypass certificate name constraints by exploiting case sensitivity in wildcard DNS SANs, allowing unauthorized access via trusted chains.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33810?
CVE-2026-33810 is a high-severity authentication bypass vulnerability in Golang Go, published on 8 Apr 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 containing excluded DNS constraints, these constraints are not correctly applied to wildcard DNS SANs which use a different case than the constraint. This only affects validation of otherwise trusted certificate chains, issued by a root CA in the VerifyOptions.Roots CertPool, or in the system certificate pool.
Which versions are affected by CVE-2026-33810?
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 | 1.26.2 |
stdlib Go | From 1.26.0-0 | 1.26.2 |
Linux distribution packages (13)
yggdrasil AlmaLinux:10 | All versions | 0.4.9.2-1.el10_2.2 |
yggdrasil-devel AlmaLinux:10 | All versions | 0.4.9.2-1.el10_2.2 |
yggdrasil Red Hat:enterprise_linux:10.2 | All versions | 0:0.4.9.2-1.el10_2.2 |
yggdrasil-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 0:0.4.9.2-1.el10_2.2 |
yggdrasil-debugsource Red Hat:enterprise_linux:10.2 | All versions | 0:0.4.9.2-1.el10_2.2 |
yggdrasil-devel Red Hat:enterprise_linux:10.2 | All versions | 0:0.4.9.2-1.el10_2.2 |
yggdrasil-examples-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 0:0.4.9.2-1.el10_2.2 |
yggdrasil Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.4.7-6.el10_0 |
yggdrasil-debuginfo Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.4.7-6.el10_0 |
yggdrasil-debugsource Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.4.7-6.el10_0 |
yggdrasil-devel Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.4.7-6.el10_0 |
yggdrasil-examples-debuginfo Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.4.7-6.el10_0 |
yggdrasil Rocky Linux:10 | All versions | 0:0.4.9.2-1.el10_2.2 |
Products include Golang Go.
How do I fix CVE-2026-33810?
Upgrade golang to 1.26.2 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-33810 being exploited?
There is no known exploitation of CVE-2026-33810 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 ALSA-2026:57126, AZL-82328, AZL-82397, BELL-CVE-2026-33810, BIT-golang-2026-33810, CLEANSTART-2026-AZ32352 and 552 more.