DETECTION OVERVIEW
Risk Factors
This vulnerability is well known and SMTP servers are often exposed to the internet. An attacker can gain control of the mail server and perform additional attacks, such as denial-of-service (DoS), permanent data loss, privilege escalation, or lateral movement attacks on the network.
Kill Chain
Risk Score
94
OpenSMTPD is an open-source mail transfer agent (MTA) that runs on Unix servers. The OpenSMTPD smtp_mailaddr() function has a vulnerability in how it validates sender and recipient mail addresses. The attacker sends a malformed SMTP message with the MAIL FROM or RCPT TO fields containing a blank domain and a malicious command instead of a valid local address. The server fills in the blank domain with a default value and passes the local address contents to the server without validation, allowing the command to run with the privileges of the daemon, which often runs as root.
Update OpenSMTPD to version 6.6.2 or later