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.
Published: 2023-12-24
Score: 5.3 Medium
EPSS: 1.6% Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Analysis and contextual insights are available on OpenCVE Cloud.

Remediation

No vendor fix or workaround currently provided.

Additional remediation guidance may be available on OpenCVE Cloud.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-3708-1 exim4 security update
Debian DSA Debian DSA DSA-5597-1 exim4 security update
Ubuntu USN Ubuntu USN USN-6611-1 Exim vulnerability
References
Link Providers
http://www.openwall.com/lists/oss-security/2023/12/24/1 cve-icon cve-icon
http://www.openwall.com/lists/oss-security/2023/12/25/1 cve-icon cve-icon
http://www.openwall.com/lists/oss-security/2023/12/29/2 cve-icon cve-icon
http://www.openwall.com/lists/oss-security/2024/01/01/1 cve-icon cve-icon
http://www.openwall.com/lists/oss-security/2024/01/01/2 cve-icon cve-icon
http://www.openwall.com/lists/oss-security/2024/01/01/3 cve-icon cve-icon
https://bugs.exim.org/show_bug.cgi?id=3063 cve-icon cve-icon
https://bugzilla.redhat.com/show_bug.cgi?id=2255852 cve-icon cve-icon
https://exim.org/static/doc/security/CVE-2023-51766.txt cve-icon cve-icon
https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html cve-icon cve-icon
https://git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5ca cve-icon cve-icon
https://git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5 cve-icon cve-icon
https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766 cve-icon cve-icon
https://lists.debian.org/debian-lts-announce/2024/01/msg00002.html cve-icon cve-icon
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/ cve-icon cve-icon
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/ cve-icon cve-icon
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/ cve-icon
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/ cve-icon
https://lwn.net/Articles/956533/ cve-icon cve-icon
https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/ cve-icon cve-icon
https://www.openwall.com/lists/oss-security/2023/12/23/2 cve-icon cve-icon
https://www.youtube.com/watch?v=V8KPV96g1To cve-icon cve-icon

Subscriptions

Debian Debian Linux
Exim Exim
Fedoraproject Extra Packages For Enterprise Linux Fedora
cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2025-11-04T18:21:35.998Z

Reserved: 2023-12-24T00:00:00.000Z

Link: CVE-2023-51766

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Modified

Published: 2023-12-24T06:15:07.673

Modified: 2025-11-04T19:16:21.973

Link: CVE-2023-51766

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses