CVE-2023-51764Postfix 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 re…
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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
- 5.3 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- mitre
- NVD analysis
- Modified
- Record last updated
- Oct 8, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
postfix postfix postfix:postfix | before 3.5.23; from 3.6.0 before 3.6.13; from 3.7.0 before 3.7.9; from 3.8.0 before 3.8.4 | NVD |
fedoraproject fedora fedoraproject:fedora | 38; 39 | NVD |
redhat enterprise_linux redhat:enterprise_linux | 8.0; 9.0 | NVD |
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/2023/12/24/1mailing-list
- http://www.openwall.com/lists/oss-security/2023/12/25/1mailing-list
- 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/vendor-advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/vendor-advisory
- 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.htmlmailing-list
- http://www.openwall.com/lists/oss-security/2024/05/09/3mailing-list
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.