{"id":"CVE-2023-51764","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 options that exist in recent versions)","summary":"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 u…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","cwe":["CWE-345"],"vendor":"postfix","product":"postfix","affected":["postfix < 3.5.23","postfix >= 3.6.0, < 3.6.13","postfix >= 3.7.0, < 3.7.9","postfix >= 3.8.0, < 3.8.4","fedora = 38","fedora = 39","enterprise_linux = 8.0","enterprise_linux = 9.0"],"patched":["postfix 3.8.4"],"published":"2023-12-24","updated":"2026-10-08","sourceUpdated":"2026-10-08T21:17:49.743","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2023-51764","references":[{"url":"http://www.openwall.com/lists/oss-security/2023/12/24/1","label":"cve@mitre.org"},{"url":"http://www.openwall.com/lists/oss-security/2023/12/25/1","label":"cve@mitre.org"},{"url":"http://www.openwall.com/lists/oss-security/2024/05/09/3","label":"cve@mitre.org"},{"url":"https://access.redhat.com/security/cve/CVE-2023-51764","label":"cve@mitre.org"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2255563","label":"cve@mitre.org"},{"url":"https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html","label":"cve@mitre.org"},{"url":"https://github.com/duy-31/CVE-2023-51764","label":"cve@mitre.org"},{"url":"https://github.com/eeenvik1/CVE-2023-51764","label":"cve@mitre.org"},{"url":"https://lists.debian.org/debian-lts-announce/2024/01/msg00020.html","label":"cve@mitre.org"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/","label":"cve@mitre.org"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/","label":"cve@mitre.org"},{"url":"https://lwn.net/Articles/956533/","label":"cve@mitre.org"},{"url":"https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/","label":"cve@mitre.org"},{"url":"https://www.openwall.com/lists/oss-security/2024/01/22/1","label":"cve@mitre.org"},{"url":"https://www.postfix.org/announcements/postfix-3.8.5.html","label":"cve@mitre.org"},{"url":"https://www.postfix.org/smtp-smuggling.html","label":"cve@mitre.org"},{"url":"https://www.youtube.com/watch?v=V8KPV96g1To","label":"cve@mitre.org"},{"url":"http://www.openwall.com/lists/oss-security/2023/12/24/1","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.openwall.com/lists/oss-security/2023/12/25/1","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.openwall.com/lists/oss-security/2024/05/09/3","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://access.redhat.com/security/cve/CVE-2023-51764","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2255563","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/duy-31/CVE-2023-51764","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/eeenvik1/CVE-2023-51764","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2024/01/msg00020.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lwn.net/Articles/956533/","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.openwall.com/lists/oss-security/2024/01/22/1","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.postfix.org/announcements/postfix-3.8.5.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.postfix.org/smtp-smuggling.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.youtube.com/watch?v=V8KPV96g1To","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd","exploit-available"],"epss":0.02635,"epssPercentile":0.85102,"exploits":{"github":4,"githubRepos":["https://github.com/duy-31/CVE-2023-51764","https://github.com/eeenvik1/CVE-2023-51764","https://github.com/d4op/CVE-2023-51764-POC"],"checkedAt":"2026-10-09T10:30:36.514Z"},"exploitAvailable":true,"ingestedAt":"2026-10-08T22:11:53.760Z","slug":"CVE-2023-51764","body":"## Overview\n\nPostfix 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.\n\n## Affected\n\n- `postfix < 3.5.23`\n- `postfix >= 3.6.0, < 3.6.13`\n- `postfix >= 3.7.0, < 3.7.9`\n- `postfix >= 3.8.0, < 3.8.4`\n- `fedora = 38`\n- `fedora = 39`\n- `enterprise_linux = 8.0`\n- `enterprise_linux = 9.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `postfix 3.8.4`","depth":"twilight","depthScore":42,"depthScoreParts":{"impact":29.2,"likelihood":0.5,"exploitation":12,"ransomware":0},"changes":[]}