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GO-2026-4866

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

Quick fix

GO-2026-4866 — stdlib: upgrade to the fixed version with the command below.

go get stdlib@v1.26.2

Details

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.

Are you affected?

Enter the version of the package you're using.

Affected packages

Go / stdlib

Introduced in: 1.26.0-0 Fixed in: 1.26.2

Fix go get stdlib@v1.26.2

References

https://go.dev/cl/763763 [FIX]
https://go.dev/issue/78332 [REPORT]
https://groups.google.com/g/golang-announce/c/0uYbvbPZRWU [WEB]