CVE-2023-51766

MEDIUM

Exim < 4.97.1 - SMTP Smuggling via LF.CR.LF Sequence

Title source: llm

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.

References (22)

Core 22

Core References

Issue Tracking, Vendor Advisory

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

Issue Tracking, Third Party Advisory

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

Broken Link

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

Technical Description

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

Patch

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

Patch

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

Mitigation, Vendor Advisory

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

View Writeup ZIP pw:eip

Third Party Advisory

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

Technical Description, Third Party Advisory

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

Issue Tracking, Mailing List, Third Party Advisory

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

Exploit

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

Mailing List, Third Party Advisory

https://lists.fedoraproject.org/archives/list/[email protected]/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/

Mailing List, Third Party Advisory

https://lists.fedoraproject.org/archives/list/[email protected]/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/

Mailing List, Third Party Advisory mailing-list

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

Mailing List, Third Party Advisory mailing-list

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

Mailing List, Mitigation, Third Party Advisory mailing-list

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

Mailing List, Third Party Advisory mailing-list

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

Mailing List, Third Party Advisory mailing-list

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

Mailing List, Third Party Advisory mailing-list

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

Mailing List, Third Party Advisory mailing-list

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

Mailing List, Third Party Advisory vendor-advisory

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

Mailing List, Third Party Advisory vendor-advisory

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

Scores

CVSS v3 5.3

EPSS 0.0107

EPSS Percentile 60.4%

Attack Vector NETWORK

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

Details

CWE

CWE-345

Status published

Products (7)

debian/debian_linux 10.0

exim/exim < 4.97.1

fedoraproject/extra_packages_for_enterprise_linux 7.0

fedoraproject/extra_packages_for_enterprise_linux 8.0

fedoraproject/extra_packages_for_enterprise_linux 9.0

fedoraproject/fedora 38

fedoraproject/fedora 39

Published Dec 24, 2023

Tracked Since Feb 18, 2026