CVE-2026-33810: Case-sensitive excludedSubtrees name constraints cause Auth Bypass in crypto/x509

Published Apr 8, 2026
·
Updated

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

Other sources

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.

— MITRE

Affected Software

10 affected componentsFixes available
go crypto/x509
Microsoft azl3 golang 1.26.1-1
Patch available
Microsoft azl3 golang 1.25.8-1
Patch available
debian/golang-1.15
1.15.15-1~deb11u4
debian/golang-1.19
1.19.8-2
debian/golang-1.24
1.24.4-11.24.13-2
debian/golang-1.25
1.25.9-1
debian/golang-1.26
1.26.2-1
Golang Go>=1.26.0<1.26.2
IBM Planning Analytics Local<=2.1.0-2.1.21

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade debian/golang-1.15 to a version that resolves this vulnerability.

    Fixed in 1.15.15-1~deb11u4
  2. Upgrade

    Upgrade debian/golang-1.19 to a version that resolves this vulnerability.

    Fixed in 1.19.8-2
  3. Upgrade

    Upgrade debian/golang-1.24 to a version that resolves this vulnerability.

    Fixed in 1.24.4-1Fixed in 1.24.13-2
  4. Upgrade

    Upgrade debian/golang-1.25 to a version that resolves this vulnerability.

    Fixed in 1.25.9-1
  5. Upgrade

    Upgrade debian/golang-1.26 to a version that resolves this vulnerability.

    Fixed in 1.26.2-1

Event History

Apr 8, 2026
CVE Published
via MITRE·01:06 AM
Data Sourced
via MITRE·01:06 AM
DescriptionWeakness
Data Sourced
via Red Hat·02:01 AM
DescriptionSeverityAffected Software
Data Sourced
via NVD·02:16 AM
RemedyDescriptionSeverityWeaknessAffected Software
Apr 11, 2026
Data Sourced
via Microsoft·08:10 AM
DescriptionSeverityWeakness
Data Sourced
via Microsoft·08:10 AM
Affected Software
Updated
via Microsoft·08:10 AM
Affected Software
Updated
via Microsoft·08:10 AM
DescriptionSeverity
Apr 19, 2026
Data Sourced
via Debian·09:56 PM
DescriptionAffected Software
Jul 9, 2026
Data Sourced
via IBM·12:00 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

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Frequently Asked Questions

1

What is the severity of CVE-2026-33810?

CVE-2026-33810 is classified as a high severity vulnerability due to its potential to allow authentication bypass in certificate verification.

2

How do I fix CVE-2026-33810?

To fix CVE-2026-33810, upgrade to the recommended versions of Golang, including 1.15.15-1~deb11u4, 1.19.8-2, 1.24.4-1, 1.25.9-1, or 1.26.2-1.

3

What products are affected by CVE-2026-33810?

CVE-2026-33810 affects the Go crypto/x509 library and specific versions of Golang and related packages.

4

What is the cause of CVE-2026-33810?

CVE-2026-33810 arises from improperly applied case-sensitive excludedSubtrees name constraints that lead to an authentication bypass in wildcard DNS SANs.

5

What are the potential impacts of CVE-2026-33810?

The potential impacts of CVE-2026-33810 include unauthorized access to systems due to authentication bypass vulnerabilities.

Company

Resources

Contact

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