smtp_mailaddr in smtp_session.c in OpenSMTPD 6.6, as used in OpenBSD 6.6 and other products, allows remote attackers to execute arbitrary commands as root via a crafted SMTP session, as demonstrated by shell metacharacters in a MAIL FROM field. This affects the "uncommented" default configuration. The issue exists because of an incorrect return value upon failure of input validation.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-7247
• openbsd/src@9dcfda0
• https://seclists.org/bugtraq/2020/Jan/51
• https://www.debian.org/security/2020/dsa-4611
• https://www.kb.cert.org/vuls/id/390745
• https://www.openbsd.org/security.html
• http://packetstormsecurity.com/files/156137/OpenBSD-OpenSMTPD-Privilege-Escalation-Code-Execution.html
• http://packetstormsecurity.com/files/156145/OpenSMTPD-6.6.2-Remote-Code-Execution.html
• http://packetstormsecurity.com/files/156249/OpenSMTPD-MAIL-FROM-Remote-Code-Execution.html
• http://packetstormsecurity.com/files/156295/OpenSMTPD-6.6.1-Local-Privilege-Escalation.html
• http://packetstormsecurity.com/files/162093/OpenBSD-OpenSMTPD-6.6-Remote-Code-Execution.html
• http://seclists.org/fulldisclosure/2020/Jan/49
• http://www.openwall.com/lists/oss-security/2020/01/28/3
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OPH4QU4DNVHA7ACFXMYFCEP5PSXXPN4E
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OPH4QU4DNVHA7ACFXMYFCEP5PSXXPN4E
• https://usn.ubuntu.com/4268-1