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Vulnerability record · CVE-2023-51765 · published 24 December 2023

CVE-2023-51765: Sendmail insufficient verification of data authenticity vulnerability

Sendmail · Sendmail

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.

5.3 CVSS 3.1 Medium EPSS 1.1% · top 36.2% CWE-345 · Insufficient verification of data authenticity
5.3CVSS 3.1 base score
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
34References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://www.openwall.com/lists/oss-security/2023/12/24/1 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/25/1 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/26/5 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/29/5 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/30/1 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/30/3 Mailing ListThird Party Advisory
https://access.redhat.com/security/cve/CVE-2023-51765 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2255869 Issue TrackingThird Party Advisory
https://bugzilla.suse.com/show_bug.cgi?id=1218351 Issue TrackingPatchThird Party Advisory
https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html Technical Description
https://github.com/freebsd/freebsd-src/commit/5dd76dd0cc19450133aa379ce0ce4a68ae07fb39#diff-afdf514b32ac88004952c11660c5 Patch
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 DescriptionThird Party Advisory
https://www.openwall.com/lists/oss-security/2023/12/21/7 Mailing ListThird Party Advisory
https://www.openwall.com/lists/oss-security/2023/12/22/7 Mailing ListThird Party Advisory
https://www.youtube.com/watch?v=V8KPV96g1To Exploit
http://www.openwall.com/lists/oss-security/2023/12/24/1 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/25/1 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/26/5 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/29/5 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/30/1 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2023/12/30/3 Mailing ListThird Party Advisory
https://access.redhat.com/security/cve/CVE-2023-51765 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2255869 Issue TrackingThird Party Advisory
https://bugzilla.suse.com/show_bug.cgi?id=1218351 Issue TrackingPatchThird Party Advisory
https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html Technical Description
https://github.com/freebsd/freebsd-src/commit/5dd76dd0cc19450133aa379ce0ce4a68ae07fb39#diff-afdf514b32ac88004952c11660c5 Patch
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 DescriptionThird Party Advisory
https://www.openwall.com/lists/oss-security/2023/12/21/7 Mailing ListThird Party Advisory
https://www.openwall.com/lists/oss-security/2023/12/22/7 Mailing ListThird Party Advisory
https://www.youtube.com/watch?v=V8KPV96g1To Exploit

Track CVE-2023-51765 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

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Source: NIST National Vulnerability Database (record CVE-2023-51765), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.