Jean-Samuel Reynaud

**Name of the Vulnerable Software and Affected Versions** Postfix version 2.1.3 **Description** The issue allows remote attackers to bypass e-mail restrictions and perform mail relaying by sending mail to an IPv6 hostname, when /proc/net/if inet6 is not available and permit mx backup is enabled in smtpd recipient restrictions. **Recommendations** For Postfix version 2.1.3, consider disabling the permit mx backup option in smtpd recipient restrictions as a temporary workaround to minimize the risk of exploitation.