UBUNTU-CVE-2023-51764

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UBUNTU-CVE-2023-51764

Summary:

Details: Postfix through 3.8.5 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 <LF>.<CR><LF> but some other popular e-mail servers do not. To prevent attack variants (by always disallowing <LF> without <CR>), a different solution is required, such as 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.

References: https://ubuntu.com/security/CVE-2023-51764, https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/, https://www.openwall.com/lists/oss-security/2023/12/21/6, https://www.postfix.org/smtp-smuggling.html, https://www.mail-archive.com/[email protected]/msg100901.html, https://www.openwall.com/lists/oss-security/2023/12/22/3, https://ubuntu.com/security/notices/USN-6591-1, https://ubuntu.com/security/notices/USN-6591-2, https://www.cve.org/CVERecord?id=CVE-2023-51764