CVE-2026-33810

HIGH

Case-sensitive excludedSubtrees name constraints cause Auth Bypass in crypto/x509

Title source: cna

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.

References (6)

https://go.dev/cl/763763

https://go.dev/issue/78332

https://groups.google.com/g/golang-announce/c/0uYbvbPZRWU

https://pkg.go.dev/vuln/GO-2026-4866

[Mailing List] http://www.openwall.com/lists/oss-security/2026/04/19/4

[Mailing List] http://www.openwall.com/lists/oss-security/2026/04/20/1

Scores

CVSS v3 8.2

EPSS 0.0001

EPSS Percentile 1.4%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

CISA SSVC

Vulnrichment

Exploitation none

Automatable yes

Technical Impact partial

Details

CWE

CWE-295

Status published

Products (2)

Go standard library/crypto/x509 1.26.0-0 - 1.26.2

golang/go 1.26.0 - 1.26.2

Published Apr 08, 2026

Tracked Since Apr 08, 2026