CVE-2023-51764
First published: Thu Dec 21 2023(Updated: )
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.
Credit: cve@mitre.org cve@mitre.org
| Affected Software | Affected Version | How to fix |
|---|---|---|
| debian/postfix | <=3.8.2-1<=3.4.23-0+deb10u1<=3.7.6-0+deb12u2<=3.5.18-0+deb11u1 | 3.8.4-1 3.7.9-0+deb12u1 3.5.23-0+deb11u1 |
| Postfix Postfix | <3.5.23 | |
| Postfix Postfix | >=3.6.0<3.6.13 | |
| Postfix Postfix | >=3.7.0<3.7.9 | |
| Postfix Postfix | >=3.8.0<3.8.4 | |
| Fedoraproject Fedora | =38 | |
| Fedoraproject Fedora | =39 | |
| Redhat Enterprise Linux | =8.0 | |
| Redhat Enterprise Linux | =9.0 | |
| redhat/postfix | <3.8.4 | 3.8.4 |
| redhat/postfix | <3.7.9 | 3.7.9 |
| redhat/postfix | <3.6.13 | 3.6.13 |
| redhat/postfix | <3.5.23 | 3.5.23 |
| ubuntu/postfix | <2.11.0-1ubuntu1.2+ | 2.11.0-1ubuntu1.2+ |
| ubuntu/postfix | <3.3.0-1ubuntu0.4+ | 3.3.0-1ubuntu0.4+ |
| ubuntu/postfix | <3.4.13-0ubuntu1.4 | 3.4.13-0ubuntu1.4 |
| ubuntu/postfix | <3.6.4-1ubuntu1.3 | 3.6.4-1ubuntu1.3 |
| ubuntu/postfix | <3.8.1-2ubuntu0.2 | 3.8.1-2ubuntu0.2 |
| ubuntu/postfix | <3.8.4-1 | 3.8.4-1 |
| ubuntu/postfix | <3.1.0-3ubuntu0.4+ | 3.1.0-3ubuntu0.4+ |
| debian/postfix | <=3.4.23-0+deb10u1 | 3.4.23-0+deb10u2 3.5.24-0+deb11u1 3.7.10-0+deb12u1 3.8.5-1 3.9.0-2 |
Remedy
Patched versions of Postfix before 3.9 require the below configs for the fix to apply: smtpd_forbid_bare_newline = normalize smtpd_forbid_bare_newline_exclusions = $mynetworks
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Reference Links
- https://www.mail-archive.com/postfix-users@postfix.org/msg100901.html
- https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/
- https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwid
- https://www.postfix.org/smtp-smuggling.html
- https://security-tracker.debian.org/tracker/CVE-2023-51764
- http://people.debian.org/~jmw
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1059230
- 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
- https://github.com/eeenvik1/CVE-2023-51764
- https://github.com/duy-31/CVE-2023-51764
- https://www.youtube.com/watch?v=V8KPV96g1To
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/
- https://lwn.net/Articles/956533/
- https://www.openwall.com/lists/oss-security/2024/01/22/1
- https://www.postfix.org/announcements/postfix-3.8.5.html
- https://lists.debian.org/debian-lts-announce/2024/01/msg00020.html
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/
- https://launchpad.net/bugs/cve/CVE-2023-51764
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=2255565
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=2255566
- https://www.postfix.org/announcements/postfix-3.8.4.html
- https://www.openwall.com/lists/oss-security/2023/12/21/6
- https://lists.debian.org/debian-stable-announce/2023/12/msg00004.html
- https://www.openwall.com/lists/oss-security/2023/12/22/3
- https://www.postfix.org/smtp-smuggling.html#back-ports
- 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
- https://nvd.nist.gov/vuln/detail/CVE-2023-51764
- https://ubuntu.com/security/CVE-2023-51764
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