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Vulnerabilities

Vulnerability · CVE-2026-27137

crypto/x509: Incorrect enforcement of email constraints in crypto/x509

Published Mar 6, 2026 · catalog updated Sep 16, 2026 · Red Hat

Check if you run it

No confirmed exploitation is on record for CVE-2026-27137. EPSS is 0.63%. Act only if a listed version of Red Hat is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.63%
Remediation
Advisory link
Affected products
cpe golang/go

A certificate validation flaw has been discovered in the golang crypto/x509 module. When verifying a certificate chain which contains a certificate containing multiple email address constraints which share common local portions but different domain portions, these constraints will not be properly applied, and only the last constraint will be considered.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe golang/go1.26.0

How to fix CVE-2026-27137

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-27137. EPSS is 0.63%. Act only if a listed version of Red Hat is installed.

Which versions are affected?

Compare what you have installed with 1.26.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-295: Improper Certificate Validation. EPSS 0.63%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 6, 2026 · NIST NVD

    Detected

    When verifying a certificate chain which contains a certificate containing multiple email address constraints which share common local portions but different domain portions, these constraints will not be properly applied, and only the last constraint will be considered.

  2. Sep 16, 2026 · NIST NVD

    Updated

    When verifying a certificate chain which contains a certificate containing multiple email address constraints which share common local portions but different domain portions, these constraints will not be properly applied, and only the last constraint will be considered.

Sources

  • CSAF AdvisoriesVendor advisoryRHSA-2026:9872:CVE-2026-27137

    A certificate validation flaw has been discovered in the golang crypto/x509 module. When verifying a certificate chain which contains a certificate containing multiple email address constraints which share common local portions but different domain portions, these constraints wil

    security.access.redhat.com
  • CVE.orgVulnerability recordCVE-2026-27137

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-27137

    30-day exploitation probability 0.6%

    first.org
  • NIST NVDVulnerability recordCVE-2026-27137

    When verifying a certificate chain which contains a certificate containing multiple email address constraints which share common local portions but different domain portions, these constraints will not be properly applied, and only the last constraint will be considered.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.