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

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Summary

CVECVE-2026-33810
StatePUBLISHED
AssignerGo
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-08 02:16:03 UTC
Updated2026-04-17 20:41:13 UTC
DescriptionWhen 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.

Risk And Classification

Primary CVSS: v3.1 8.2 HIGH from [email protected]

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

EPSS: 0.000110000 probability, percentile 0.012220000 (date 2026-04-17)

Problem Types: CWE-295 | CWE-295: Improper Certificate Validation

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
3.1ADPDECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Golang Go All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Go Standard Library Crypto/x509 affected 1.26.0-0 1.26.2 semver Not specified

References

ReferenceSourceLinkTags
pkg.go.dev/vuln/GO-2026-4866 [email protected] pkg.go.dev Vendor Advisory
groups.google.com/g/golang-announce/c/0uYbvbPZRWU [email protected] groups.google.com Release Notes, Mailing List
go.dev/issue/78332 [email protected] go.dev Issue Tracking
go.dev/cl/763763 [email protected] go.dev Patch
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Riyas from Saintgits College of Engineering (en)

CNA: k1rnt (en)

CNA: @1seal (en)

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