Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2023-51764

CVE-2023-51764MEDIUM

n/a n/a — Postfix through 3.8.5 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehl…

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  N  L  N    5.3   .0263   85.3     —

AFFECTED
  Product  Versions  Fixed
  n/a      n/a –     —

TIMELINE
  Dec 24  Reserved by mitre
  Dec 24  Published (CNA: mitre)
  Oct 8   ENRICHED — CVE-2023-51764. Received CVSS 5.3 and CPE data from NVD.
  Oct 8   EXPLOIT PUBLISHED — CVE-2023-51764. Public exploit reference added.

CWE-345 · CNA: mitre · CVSS v3.1 · 19 references · NVD 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.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
December 24, 2023	Reserved	Reserved by mitre
December 24, 2023	Published	Published (CNA: mitre)
October 8, 2026	ENRICHED	ENRICHED — CVE-2023-51764. Received CVSS 5.3 and CPE data from NVD.
October 8, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2023-51764. Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
n/a	n/a	—	n/a	—

Weaknesses

CWE-345

References (19)

http://www.openwall.com/lists/oss-security/2023/12/24/1 [Mailing List, Third Party Advisory]
http://www.openwall.com/lists/oss-security/2023/12/25/1 [Mailing List, Third Party Advisory]
http://www.openwall.com/lists/oss-security/2024/05/09/3
https://access.redhat.com/security/cve/CVE-2023-51764 [Third Party Advisory]
https://bugzilla.redhat.com/show_bug.cgi?id=2255563 [Issue Tracking, Third Party Advisory]
https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html [Technical Description]
https://github.com/duy-31/CVE-2023-51764 [Exploit, Third Party Advisory]
https://github.com/eeenvik1/CVE-2023-51764 [Exploit, Third Party Advisory]
https://lists.debian.org/debian-lts-announce/2024/01/msg00020.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/
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://lwn.net/Articles/956533/
https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/ [Technical Description, Third Party Advisory]
https://www.openwall.com/lists/oss-security/2024/01/22/1
https://www.postfix.org/announcements/postfix-3.8.5.html
https://www.postfix.org/smtp-smuggling.html [Exploit, Mitigation, Vendor Advisory]
https://www.youtube.com/watch?v=V8KPV96g1To [Exploit]

Authoritative record: CVE-2023-51764 at cve.org

Weaknesses: CWE-345

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2023-51764 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.