OpenSMTPD before 6.6.4 allows remote code execution because of an out-of-bounds read in mta_io in mta_session.c for multi-line replies. Although this vulnerability affects the client side of OpenSMTPD, it is possible to attack a server because the server code launches the client code during bounce handling.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-8794
• https://lists.fedoraproject.org/archives/list/[email protected]/message/OPH4QU4DNVHA7ACFXMYFCEP5PSXXPN4E/
• https://usn.ubuntu.com/4294-1/
• https://www.debian.org/security/2020/dsa-4634
• https://www.openbsd.org/security.html
• https://www.openwall.com/lists/oss-security/2020/02/24/5
• http://packetstormsecurity.com/files/156633/OpenSMTPD-Out-Of-Bounds-Read-Local-Privilege-Escalation.html
• http://seclists.org/fulldisclosure/2020/Feb/32
• http://www.openwall.com/lists/oss-security/2020/02/26/1
• http://www.openwall.com/lists/oss-security/2020/03/01/1
• http://www.openwall.com/lists/oss-security/2020/03/01/2
• http://www.openwall.com/lists/oss-security/2021/05/04/7