🛡️ CVE-2023-51764
🟡 CVSS 5.3 — Medium ⚠️ Exploit Public CWE-345 NVD
5.3
CVSS Score
0 Low4 Medium7 High9 Critical10

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 . 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.

Details

Severity MEDIUM
CVSS Score 5.3
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CWE CWE-345
Public Exploit ⚠️ Yes
Source NVD
Published 2023-12-24
Updated 2026-06-08
Modified 2025-11-04
Fix URL N/A

Affected Packages

Software From version Fixed in
enterprise-linux — —
fedora — —
postfix 3.8.0 3.8.4

References

Mailing List, Third Party Advisory 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
Issue Tracking, Third Party Advisory https://bugzilla.redhat.com/show_bug.cgi?id=2255563
Exploit, Third Party Advisory https://github.com/duy-31/CVE-2023-51764
Exploit, Third Party Advisory https://github.com/eeenvik1/CVE-2023-51764
Exploit, Mitigation, Vendor Advisory https://www.postfix.org/smtp-smuggling.html
Mailing List, Third Party Advisory 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
Issue Tracking, Third Party Advisory https://bugzilla.redhat.com/show_bug.cgi?id=2255563
Exploit, Third Party Advisory https://github.com/duy-31/CVE-2023-51764
Exploit, Third Party Advisory https://github.com/eeenvik1/CVE-2023-51764
Exploit, Mitigation, Vendor Advisory https://www.postfix.org/smtp-smuggling.html

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