CVE-2023-51766

Published: Dec 24, 2023Modified: Nov 4, 2025

5.3

Vector

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

Exploitability: 3.9 / Impact: 1.4

Source: NVD

Description

Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING 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 Exim supports <LF>.<CR><LF> but some other popular e-mail servers do not.

Affected (7)

Products: Exim: Exim · Fedoraproject: Extra Packages For Enterprise Linux, Fedora · Debian: Debian Linux

Exim

1 product

Exim

Fedoraproject

2 products

Extra Packages For Enterprise Linux

Fedora

Debian

1 product

Debian Linux

Configuration A

1 vulnerable

Vulnerable Software	Affected Versions
Exim Exim	Before 4.97.1

Configuration B

5 vulnerable

Vulnerable Software	Affected Versions
Fedoraproject Extra Packages For Enterprise Linux	Version 7.0
Fedoraproject Extra Packages For Enterprise Linux	Version 8.0
Fedoraproject Extra Packages For Enterprise Linux	Version 9.0
Fedoraproject Fedora	Version 38
Fedoraproject Fedora	Version 39

Configuration C

1 vulnerable

Vulnerable Software	Affected Versions
Debian Debian Linux	Version 10.0

Related CWEs

CWE-345

Insufficient Verification of Data Authenticity

The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.

References (42)

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

Source: cve@mitre.org

Mailing ListThird Party Advisory

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

Source: cve@mitre.org

Mailing ListThird Party Advisory

http://www.openwall.com/lists/oss-security/2023/12/29/2

Source: cve@mitre.org

Mailing ListMitigationThird Party Advisory

http://www.openwall.com/lists/oss-security/2024/01/01/1

Source: cve@mitre.org

Mailing ListThird Party Advisory

http://www.openwall.com/lists/oss-security/2024/01/01/2

Source: cve@mitre.org

Mailing ListThird Party Advisory

http://www.openwall.com/lists/oss-security/2024/01/01/3

Source: cve@mitre.org

Mailing ListThird Party Advisory

https://bugs.exim.org/show_bug.cgi?id=3063

Source: cve@mitre.org

Issue TrackingVendor Advisory

https://bugzilla.redhat.com/show_bug.cgi?id=2255852

Source: cve@mitre.org

Issue TrackingThird Party Advisory

https://exim.org/static/doc/security/CVE-2023-51766.txt

Source: cve@mitre.org

Broken Link

https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html

Source: cve@mitre.org

Technical Description

https://git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5ca

Source: cve@mitre.org

Patch

https://git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5

Source: cve@mitre.org

Patch

https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766

Source: cve@mitre.org

MitigationVendor Advisory

https://lists.debian.org/debian-lts-announce/2024/01/msg00002.html

Source: cve@mitre.org

Mailing ListThird Party Advisory

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/

Source: cve@mitre.org

Mailing ListThird Party Advisory

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/

Source: cve@mitre.org

Mailing ListThird Party Advisory

https://lwn.net/Articles/956533/

Source: cve@mitre.org

Third Party Advisory

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

Source: cve@mitre.org

Technical DescriptionThird Party Advisory

https://www.openwall.com/lists/oss-security/2023/12/23/2

Source: cve@mitre.org

Issue TrackingMailing ListThird Party Advisory

https://www.youtube.com/watch?v=V8KPV96g1To

Source: cve@mitre.org

Exploit

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