HOME VULNERABILITIESCVE-2023-51765

MEDIUM

CVE-2023-51765

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

5.3

CVSS v3.1

Official Description

sendmail through 8.17.2 allows SMTP smuggling in certain configurations. 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 sendmail supports <LF>.<CR><LF> but some other popular e-mail servers do not. This is resolved in 8.18 and later versions with 'o' in srv_features.

Technical Analysis

CVE-2023-51765 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

freebsd1 product(s)

freebsd

Red Hat1 product(s)

enterprise linux

sendmail1 product(s)

sendmail

Source: NVD CPE · 4 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

PATCHhttps://bugzilla.suse.com/show_bug.cgi?id=1218351

PATCHhttps://github.com/freebsd/freebsd-src/commit/5dd76dd0cc19450133aa379ce0ce4a68ae07fb39#diff-afdf514b32ac88004952c11660c57bc96c3d8b2234007c1cbd8d7ed7fd7935cc

PATCHhttps://bugzilla.suse.com/show_bug.cgi?id=1218351

PATCHhttps://github.com/freebsd/freebsd-src/commit/5dd76dd0cc19450133aa379ce0ce4a68ae07fb39#diff-afdf514b32ac88004952c11660c57bc96c3d8b2234007c1cbd8d7ed7fd7935cc

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

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

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/26/5

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/29/5

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/30/1

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/30/3

ADVISORYhttps://access.redhat.com/security/cve/CVE-2023-51765

ADVISORYhttps://bugzilla.redhat.com/show_bug.cgi?id=2255869

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

ADVISORYhttps://www.openwall.com/lists/oss-security/2023/12/21/7

ADVISORYhttps://www.openwall.com/lists/oss-security/2023/12/22/7

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

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

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/26/5

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/29/5

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/30/1

ADVISORYhttp://www.openwall.com/lists/oss-security/2023/12/30/3

ADVISORYhttps://access.redhat.com/security/cve/CVE-2023-51765

ADVISORYhttps://bugzilla.redhat.com/show_bug.cgi?id=2255869

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

ADVISORYhttps://www.openwall.com/lists/oss-security/2023/12/21/7

ADVISORYhttps://www.openwall.com/lists/oss-security/2023/12/22/7

All References (34)

→

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/2023/12/26/5Mailing List · Third Party Advisory

→

http://www.openwall.com/lists/oss-security/2023/12/29/5Mailing List · Third Party Advisory

→

http://www.openwall.com/lists/oss-security/2023/12/30/1Mailing List · Third Party Advisory

→

http://www.openwall.com/lists/oss-security/2023/12/30/3Mailing List · Third Party Advisory

→

https://access.redhat.com/security/cve/CVE-2023-51765Third Party Advisory

→

https://bugzilla.redhat.com/show_bug.cgi?id=2255869Issue Tracking · Third Party Advisory

→

https://bugzilla.suse.com/show_bug.cgi?id=1218351Issue Tracking · Patch · Third Party Advisory

→

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

→

https://github.com/freebsd/freebsd-src/commit/5dd76dd0cc19450133aa379ce0ce4a68ae07fb39#diff-afdf514b32ac88004952c11660c57bc96c3d8b2234007c1cbd8d7ed7fd7935ccPatch

→

https://lists.debian.org/debian-lts-announce/2024/06/msg00004.html

→

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/2023/12/21/7Mailing List · Third Party Advisory

Quick Facts

CVE IDCVE-2023-51765

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-2023-51765 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.

← All Vulnerabilities·Search for CVE-2023-51765·NVD