A critical vulnerability has been found in OpenSMTPD that if exploited could allow an attacker to execute arbitrary code.
The flaw, CVE-20207247, was discovered by Qualys Research Labs and affects OpenSMTPD version 6.6, which does not properly sanitize user input which could lead to a local attacker being able to to escalate their privileges, and allow either a local or remote attacker to execute arbitrary code as root.
The open-source OpenSMTPD’s smtp_mailaddr() function is responsible for validating sender and recipient mail addresses. The problem is that if the local part of an address is invalid and the domain name is empty the software will automatically add a domain name instead of just failing because of the invalid local address. This will allow the invalid local address to pass through the function without validation.
This can be triggered if an attacker sends a malformed address, as described above, which will bypass the smtp_mailaddr() validation and execute arbitrary code. This ability could then be used by the malicious actor to execute arbitrary code.
The Carnegie Mellon University Software Engineering Institute is recommending users upgrade to OpenSMTPD version 6.6.2p1.
