HOME VULNERABILITIESCVE-2023-51764

MEDIUM

CVE-2023-51764

CWE-345Published: December 24, 2023· Updated: Jun 17, 2026

5.3

CVSS v3.1

Official 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.

Technical Analysis

CVE-2023-51764 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

CVSS v3.1 Vector Breakdown

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges Req.None

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected Vendors & Products

Fedora1 product(s)

fedora

postfix1 product(s)

postfix

Red Hat1 product(s)

enterprise linux

Source: NVD CPE · 5 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time

Offensive Security exploit database

GitHub PoC Search

Community PoC repositories

Rapid7 / Metasploit

Metasploit module search

Security advisories & exploits

Official NIST entry

CVE Program entry

External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/24/1

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/25/1

ADVISORYhttps://access.redhat.com/security/cve/CVE-2023-51764

ADVISORYhttps://bugzilla.redhat.com/show_bug.cgi?id=2255563

ADVISORYhttps://github.com/duy-31/CVE-2023-51764

ADVISORYhttps://github.com/eeenvik1/CVE-2023-51764

ADVISORYhttps://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/

ADVISORYhttps://www.postfix.org/smtp-smuggling.html

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/24/1

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/25/1

ADVISORYhttps://access.redhat.com/security/cve/CVE-2023-51764

ADVISORYhttps://bugzilla.redhat.com/show_bug.cgi?id=2255563

ADVISORYhttps://github.com/duy-31/CVE-2023-51764

ADVISORYhttps://github.com/eeenvik1/CVE-2023-51764

ADVISORYhttps://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/

ADVISORYhttps://www.postfix.org/smtp-smuggling.html

All References (36)

→

http://www.openwall.com/lists/oss-security/2023/12/24/1Mailing List · Third Party Advisory

→

http://www.openwall.com/lists/oss-security/2023/12/25/1Mailing List · Third Party Advisory

→

http://www.openwall.com/lists/oss-security/2024/05/09/3

→

https://access.redhat.com/security/cve/CVE-2023-51764Third Party Advisory

→

https://bugzilla.redhat.com/show_bug.cgi?id=2255563Issue Tracking · Third Party Advisory

→

https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.htmlTechnical Description

→

https://github.com/duy-31/CVE-2023-51764Exploit · Third Party Advisory

→

https://github.com/eeenvik1/CVE-2023-51764Exploit · 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://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

Quick Facts

CVE IDCVE-2023-51764

CVSS Score5.3 / 10

SeverityMEDIUM

WeaknessCWE-345

CISA KEVNo

Affected3 vendor(s)

PublishedDec 24, 2023

Related CVEs (CWE-345)

Recommended Actions

→Apply vendor patches immediately
→Monitor CVE-2023-51764 in threat intel feeds
→Review IDS/IPS signatures for exploitation attempts

Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.

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