CVE-2023-51766

MEDIUM EPSS 60.7%

Published Dec 24, 20232y ago · Modified Jun 17, 20262w ago

5.3 CVSS 3.1

Medium

Published Dec 24, 2023 2y ago

Last Modified Jun 17, 2026 2w ago

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.

CVSS Details

Base Score

5.3

Exploitability

3.9

Impact

1.4

Vector string

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

Attack Vector Network

Attack Complexity Low

Privileges Required None

User Interaction None

Scope Unchanged

Confidentiality None

Integrity Low

Availability None

Threat Intelligence

EPSS Exploit Probability

60.7% percentile

Exploit & Patch Status

Public Exploit Known

Patch Available

Weaknesses 1

CWE-345

Affected Products 7

Vendor	Product	Version	Range
exim	exim	*	<4.97.1
fedoraproject	extra_packages_for_enterprise_linux	7.0	any
fedoraproject	extra_packages_for_enterprise_linux	8.0	any
fedoraproject	extra_packages_for_enterprise_linux	9.0	any
fedoraproject	fedora	38	any
fedoraproject	fedora	39	any
debian	debian_linux	10.0	any

References 22

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

Mailing ListThird Party Advisory
openwall.com http://www.openwall.com/lists/oss-security/2023/12/25/1

Mailing ListThird Party Advisory
openwall.com http://www.openwall.com/lists/oss-security/2023/12/29/2

Mailing ListMitigationThird Party Advisory
openwall.com http://www.openwall.com/lists/oss-security/2024/01/01/1

Mailing ListThird Party Advisory
openwall.com http://www.openwall.com/lists/oss-security/2024/01/01/2

Mailing ListThird Party Advisory
openwall.com http://www.openwall.com/lists/oss-security/2024/01/01/3

Mailing ListThird Party Advisory
bugs.exim.org https://bugs.exim.org/show_bug.cgi?id=3063

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

Issue TrackingThird Party Advisory
exim.org https://exim.org/static/doc/security/CVE-2023-51766.txt

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

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

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

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

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

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

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

Mailing ListThird Party Advisory
lists.fedoraproject.org https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/
lists.fedoraproject.org https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/
lwn.net https://lwn.net/Articles/956533/

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

Technical DescriptionThird Party Advisory
openwall.com https://www.openwall.com/lists/oss-security/2023/12/23/2

Issue TrackingMailing ListThird Party Advisory
youtube.com https://www.youtube.com/watch?v=V8KPV96g1To

Exploit

Remediation

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

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

Patch