CVE-2023-51764 Information

Description

Postfix through 3.8.4 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehlo_keywords=chunking (or certain other options that exist in recent versions). Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address allowing bypass of an SPF protection mechanism. This occurs because Postfix supports . but some other popular e-mail servers do not. To prevent attack variants (by always disallowing without ) a different solution is required: the smtpd_forbid_bare_newline=yes option with a Postfix minimum version of 3.5.23 3.6.13 3.7.9 3.8.4 or 3.9.

Reference

https://www.postfix.org/smtp-smuggling.html https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/ http://www.openwall.com/lists/oss-security/2023/12/24/1 http://www.openwall.com/lists/oss-security/2023/12/25/1 https://bugzilla.redhat.com/show_bug.cgi?id=2255563 https://access.redhat.com/security/cve/CVE-2023-51764 https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html