{"id":"CVE-2023-51764","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 \u003cLF\u003e.\u003cCR\u003e\u003cLF\u003e but some other popular e-mail servers do not. To prevent attack variants (by always disallowing \u003cLF\u003e without \u003cCR\u003e), 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.","modified":"2026-04-16T04:32:28.156999137Z","published":"2023-12-24T05:15:08.273Z","related":["ALSA-2024:9243","SUSE-SU-2023:4981-1","SUSE-SU-2024:0012-1","SUSE-SU-2024:1149-1","openSUSE-SU-2024:13538-1"],"references":[{"type":"WEB","url":"https://www.openwall.com/lists/oss-security/2024/01/22/1"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/"},{"type":"WEB","url":"https://www.postfix.org/announcements/postfix-3.8.5.html"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2024/01/msg00020.html"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/"},{"type":"WEB","url":"http://www.openwall.com/lists/oss-security/2024/05/09/3"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/"},{"type":"WEB","url":"https://lwn.net/Articles/956533/"},{"type":"ADVISORY","url":"http://www.openwall.com/lists/oss-security/2023/12/25/1"},{"type":"ADVISORY","url":"http://www.openwall.com/lists/oss-security/2023/12/24/1"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2023-51764"},{"type":"ADVISORY","url":"https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2255563"},{"type":"ARTICLE","url":"https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html"},{"type":"EVIDENCE","url":"https://github.com/eeenvik1/CVE-2023-51764"},{"type":"EVIDENCE","url":"https://www.youtube.com/watch?v=V8KPV96g1To"},{"type":"EVIDENCE","url":"https://github.com/duy-31/CVE-2023-51764"},{"type":"EVIDENCE","url":"https://www.postfix.org/smtp-smuggling.html"}],"affected":[{"database_specific":{"unresolved_ranges":[{"events":[{"introduced":"0"},{"fixed":"3.5.23"}]},{"events":[{"introduced":"3.6.0"},{"fixed":"3.6.13"}]},{"events":[{"introduced":"3.7.0"},{"fixed":"3.7.9"}]},{"events":[{"introduced":"3.8.0"},{"fixed":"3.8.4"}]},{"events":[{"introduced":"0"},{"last_affected":"38"}]},{"events":[{"introduced":"0"},{"last_affected":"39"}]},{"events":[{"introduced":"0"},{"last_affected":"8.0"}]},{"events":[{"introduced":"0"},{"last_affected":"9.0"}]}],"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-51764.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}