CVE-2009-4565: sendmail before 8.14.4 does not properly handle a '\0' character in a Common Name (CN) field of an X.509 ce...

Security readout for executives and security teams

This is an old sendmail certificate-validation flaw. A malicious certificate containing a null character in the Common Name could make sendmail trust the wrong SMTP server or wrongly accept a client certificate, undermining TLS identity checks and access restrictions. Exposure is most likely on legacy systems running sendmail before 8.14.4, especially where SMTP over TLS or client certificate-based access controls are used. Treat as high priority for any remaining legacy sendmail deployment using TLS trust decisions. The age lowers likelihood in modern environments, but affected systems may permit impersonation or unauthorized SMTP access. Mitigation focus: Upgrade sendmail to 8.14.4 or later where available.; Apply vendor security updates from the affected operating system distribution.; Review vendor advisories for platform-specific fixed package versions..

Prepared

Jun 28, 2026, 09:59 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.