Disclosure 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 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 . but some other popular e-mail servers do not. To prevent attack variants (by always disallowing without ), 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.
Source-reported weakness categories
CWE-345
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
NIST National Vulnerability Database · NVD-CVE-2023-51764
Open original source · Updated Oct 08, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
| Vendor | Product / association | Version / bounds |
|---|---|---|
| postfix | postfix | * {"versionStartIncluding":"3.8.0","versionEndExcluding":"3.8.4"} |
| fedoraproject | fedora | 38 |
| fedoraproject | fedora | 39 |
| redhat | enterprise_linux | 8.0 |
| redhat | enterprise_linux | 9.0 |
Original records & references
- NIST NVD record
- CVE Program record
- access.redhat.com — Third Party Advisory
- bugzilla.redhat.com — Issue Tracking, Third Party Advisory
- fahrplan.events.ccc.de — Technical Description
- github.com — Exploit, Third Party Advisory
- github.com — Exploit, Third Party Advisory
- lists.debian.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lwn.net
- sec-consult.com — Technical Description, Third Party Advisory
- www.openwall.com
- www.postfix.org
- www.postfix.org — Exploit, Mitigation, Vendor Advisory
- www.youtube.com — Exploit
- access.redhat.com — Third Party Advisory
- bugzilla.redhat.com — Issue Tracking, Third Party Advisory
- fahrplan.events.ccc.de — Technical Description
- github.com — Exploit, Third Party Advisory
- github.com — Exploit, Third Party Advisory
- lists.debian.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lwn.net
- sec-consult.com — Technical Description, Third Party Advisory
- www.openwall.com
- www.postfix.org
- www.postfix.org — Exploit, Mitigation, Vendor Advisory
- www.youtube.com — Exploit
PUBLISHED 2023-12-24T00:15:08-05:00
MODIFIED 2026-10-08T17:17:49-04:00
INGESTED 2026-10-10T20:50:21-04:00