CVE-2023-51765

Public Exploit

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.

Category

5.3
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 1.09% Top 25%
Third-Party Advisory openwall.com Third-Party Advisory openwall.com Third-Party Advisory openwall.com Third-Party Advisory openwall.com Third-Party Advisory openwall.com Third-Party Advisory openwall.com Third-Party Advisory redhat.com Third-Party Advisory redhat.com Third-Party Advisory suse.com Third-Party Advisory sec-consult.com Third-Party Advisory openwall.com Third-Party Advisory openwall.com
Affected: n/a n/a
Published at:
Updated at:

References

Link Tags
https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/ third party advisory technical description
https://www.openwall.com/lists/oss-security/2023/12/22/7 third party advisory mailing list
https://www.openwall.com/lists/oss-security/2023/12/21/7 third party advisory mailing list
https://github.com/freebsd/freebsd-src/commit/5dd76dd0cc19450133aa379ce0ce4a68ae07fb39#diff-afdf514b32ac88004952c11660c57bc96c3d8b2234007c1cbd8d7ed7fd7935cc patch
http://www.openwall.com/lists/oss-security/2023/12/24/1 third party advisory mailing list
http://www.openwall.com/lists/oss-security/2023/12/25/1 third party advisory mailing list
https://bugzilla.suse.com/show_bug.cgi?id=1218351 patch third party advisory issue tracking
https://bugzilla.redhat.com/show_bug.cgi?id=2255869 third party advisory issue tracking
https://access.redhat.com/security/cve/CVE-2023-51765 third party advisory
https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html technical description
http://www.openwall.com/lists/oss-security/2023/12/26/5 third party advisory mailing list
http://www.openwall.com/lists/oss-security/2023/12/29/5 third party advisory mailing list
http://www.openwall.com/lists/oss-security/2023/12/30/3 third party advisory mailing list
http://www.openwall.com/lists/oss-security/2023/12/30/1 third party advisory mailing list
https://www.youtube.com/watch?v=V8KPV96g1To exploit
https://lwn.net/Articles/956533/
https://lists.debian.org/debian-lts-announce/2024/06/msg00004.html mailing list

Frequently Asked Questions

What is the severity of CVE-2023-51765?
CVE-2023-51765 has been scored as a medium severity vulnerability.
How to fix CVE-2023-51765?
To fix CVE-2023-51765, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2023-51765 being actively exploited in the wild?
It is possible that CVE-2023-51765 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~1% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
This platform uses data from the NIST NVD, MITRE CVE, MITRE CWE, First.org and CISA KEV but is not endorsed or certified by these entities. CVE is a registred trademark of the MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. CWE is a registred trademark of the MITRE Corporation and the authoritative source of CWE content is MITRE's CWE web site.
© 2025 Under My Watch. All Rights Reserved.