{"id":"CVE-2023-51764","state":"PUBLISHED","title":"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 optio","description":"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.","publishedAt":"2023-12-24T00:00:00.000Z","updatedAt":"2026-10-08T21:03:31.129Z","severity":null,"assigner":"mitre","products":["n/a n/a"],"affected":[{"vendor":"n/a","product":"n/a","versions":[{"version":"n/a","status":"affected"}]}],"references":["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","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","http://www.openwall.com/lists/oss-security/2024/05/09/3","https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/","https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/"],"weaknesses":[],"ingestedAt":"2026-10-29T20:06:33.064Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2023/51xxx/CVE-2023-51764.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2023-51764","state":"PUBLISHED","datePublished":"2023-12-24T00:00:00.000Z","dateUpdated":"2026-10-08T21:03:31.129Z","assignerShortName":"mitre","assignerOrgId":"8254265b-2729-46b6-b9e3-3dfca2d5bfca","dateReserved":"2023-12-24T00:00:00.000Z"},"containers":{"cna":{"descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"n/a","product":"n/a","versions":[{"version":"n/a","status":"affected"}]}],"references":[{"url":"https://www.postfix.org/smtp-smuggling.html"},{"url":"https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/"},{"url":"http://www.openwall.com/lists/oss-security/2023/12/24/1","name":"[oss-security] 20231224 Re: Re: New SMTP smuggling attack","tags":["mailing-list"]},{"url":"http://www.openwall.com/lists/oss-security/2023/12/25/1","name":"[oss-security] 20231225 Re: Re: New SMTP smuggling 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