Vulnerability · CVE-2026-27137
crypto/x509: Incorrect enforcement of email constraints in crypto/x509
Published Mar 6, 2026 · corrected/updated Sep 16, 2026 · Red Hat go · evidence confidence high
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.
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-27137 is a high public vulnerability record for Red Hat go. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether Red Hat go is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: golang/go (1.26.0). Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 7.5, EPSS 0.6%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-295. Sources contributing to this record: csaf, cve_org, epss, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
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.
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.
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.
Affected
- cpe golang/go1.26.0
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