CVE-2026-33810

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

CVSS 7.5 HIGHEPSS 0.3%

Vexday Risk Score

21Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 7.5EPSS 0.3%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

08 Apr 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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.

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

Affected products

Go standard library · crypto/x509

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References

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 http://www.openwall.com/lists/oss-security/2026/04/19/4 http://www.openwall.com/lists/oss-security/2026/04/20/1