CVE-2026-27137
HIGHCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
3Description
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.
Analysis
Improper validation of multi-constraint email certificates allows attackers to bypass certificate chain verification by exploiting a logic error that only processes the final constraint when multiple constraints share common local portions. This affects any system relying on certificate validation for email authentication, enabling an attacker to present a malicious certificate that would normally be rejected. …
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Remediation
Within 24 hours: Inventory all systems using certificate-based authentication with email constraints and assess exposure. Within 7 days: Implement compensating controls such as additional authentication factors, enhanced logging/monitoring of certificate validation events, and restrict certificate issuance policies. …
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