{"cve":"CVE-2023-51764","nvd":{"published":"2023-12-24T05:15:08.273","modified":"2026-10-08T21:17:49.743","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3},"cwes":["CWE-345"],"references":["http://www.openwall.com/lists/oss-security/2023/12/24/1","http://www.openwall.com/lists/oss-security/2023/12/25/1","http://www.openwall.com/lists/oss-security/2024/05/09/3","https://access.redhat.com/security/cve/CVE-2023-51764","https://bugzilla.redhat.com/show_bug.cgi?id=2255563"],"products":["fedoraproject:fedora","postfix:postfix","redhat:enterprise_linux"],"source":"nvd","synced_at":"2026-10-19T21:43:38.875533635+00:00"},"epss":{"cve":"CVE-2023-51764","score":0.02635,"percentile":0.85434,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}