CVE-2023-51766

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.

• CWE-345

• http://www.openwall.com/lists/oss-security/2023/12/24/1Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2023/12/25/1Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2023/12/29/2Mailing List, Mitigation, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2024/01/01/1Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2024/01/01/2Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2024/01/01/3Mailing List, Third Party Advisory
• https://bugs.exim.org/show_bug.cgi?id=3063Issue Tracking, Vendor Advisory
• https://bugzilla.redhat.com/show_bug.cgi?id=2255852Issue Tracking, Third Party Advisory
• https://exim.org/static/doc/security/CVE-2023-51766.txtBroken Link
• https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.htmlTechnical Description
• https://git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5caPatch
• https://git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5Patch
• https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766Mitigation, Vendor Advisory
• https://lists.debian.org/debian-lts-announce/2024/01/msg00002.htmlMailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/Mailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/Mailing List, Third Party Advisory
• https://lwn.net/Articles/956533/Third Party Advisory
• https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/Technical Description, Third Party Advisory
• https://www.openwall.com/lists/oss-security/2023/12/23/2Issue Tracking, Mailing List, Third Party Advisory
• https://www.youtube.com/watch?v=V8KPV96g1ToExploit
• http://www.openwall.com/lists/oss-security/2023/12/24/1Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2023/12/25/1Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2023/12/29/2Mailing List, Mitigation, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2024/01/01/1Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2024/01/01/2Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2024/01/01/3Mailing List, Third Party Advisory
• https://bugs.exim.org/show_bug.cgi?id=3063Issue Tracking, Vendor Advisory
• https://bugzilla.redhat.com/show_bug.cgi?id=2255852Issue Tracking, Third Party Advisory
• https://exim.org/static/doc/security/CVE-2023-51766.txtBroken Link
• https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.htmlTechnical Description
• https://git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5caPatch
• https://git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5Patch
• https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766Mitigation, Vendor Advisory
• https://lists.debian.org/debian-lts-announce/2024/01/msg00002.htmlMailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/Mailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/Mailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/
• https://lwn.net/Articles/956533/Third Party Advisory
• https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/Technical Description, Third Party Advisory
• https://www.openwall.com/lists/oss-security/2023/12/23/2Issue Tracking, Mailing List, Third Party Advisory
• https://www.youtube.com/watch?v=V8KPV96g1ToExploit

Published

Dec 24, 2023

Last Modified

Jun 17, 2026

Status

Modified

• Same Subject, Wrong User: A Cross-Issuer Account Takeover in n8nStrix found an identity-binding bug in n8n's token-exchange flow enabling account takeover.
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