Go crypto/x509 excluded DNS constraints wildcard case validation bypass
CVE-2026-33810 is a certificate validation flaw in Go 1.26's crypto/x509 component. When verifying a certificate chain that contains excluded DNS name constraints, the verification logic does not correctly apply those constraints to wildcard DNS Subject Alternative Names when the wildcard SAN uses different letter casing than the excluded constraint. As described in the provided content, a certificate containing a SAN such as "*.example.com" can evade an excluded DNS constraint such as "EXAMPLE.COM" because the constraint comparison is handled incorrectly for this wildcard-and-case combination. The issue affects validation of otherwise trusted certificate chains anchored by a root CA present in VerifyOptions.Roots or in the system certificate pool.
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A certificate validation bypass vulnerability in Go's crypto/x509 library caused by incorrect application of excluded DNS constraints to wildcard DNS SANs with different casing.
A vulnerability in Go 1.26 crypto/x509 where excluded DNS constraints are not properly applied to wildcard domains.
A certificate chain validation flaw in Go 1.26 where excluded DNS constraints are not correctly enforced against wildcard DNS SANs when case differs, potentially allowing otherwise trusted certificate chains to bypass intended DNS constraint checks.
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