CVE-2023-51766
published 2023-12-24CVE-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…
PriorityP429medium5.3CVSS 3.1
AVNACLPRNUINSUCNILAN
EPSS
1.07%
60.7th percentile
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 . but some other popular e-mail servers do not.
Affected
9 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | debian_linux | — | — |
| debian | exim4 | < exim4 4.96-15+deb12u4 (bookworm) | exim4 4.96-15+deb12u4 (bookworm) |
| exim | exim | < 4.97.1 | 4.97.1 |
| fedoraproject | extra_packages_for_enterprise_linux | — | — |
| fedoraproject | extra_packages_for_enterprise_linux | — | — |
| fedoraproject | extra_packages_for_enterprise_linux | — | — |
| fedoraproject | fedora | — | — |
| fedoraproject | fedora | — | — |
| ubuntu | exim4 | — | — |
CVSS provenance
nvdv3.15.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
osv5.3MEDIUM
vendor_debian5.3MEDIUM
vendor_ubuntu5.3MEDIUM
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Ubuntu
Exim vulnerabilities
vendor_ubuntu·2026-06-03·CVSS 5.3
CVE-2026-40687 [MEDIUM] Exim vulnerabilities
Title: Exim vulnerabilities
Summary: Several security issues were fixed in Exim.
Timo Longin discovered that Exim incorrectly handled certain SMTP messages
in PIPELINING/CHUNKING configurations. A remote attacker could possibly use
this issue to perform SMTP smuggling. This issue only affected Ubuntu
14.04 LTS. (CVE-2023-51766)
It was discovered that Exim incorrectly handled certain malformed JSON
data in headers. A remote attacker could possibly use this issue to crash
Exim, resulting in a denial of service, or execute arbitrary code. This
issue only affected Ubuntu 20.04 LTS. (CVE-2026-40685)
It was discovered that Exim incorrectly handled certain malformed UTF-8
headers. A remote attacker could possibly use this issue to obtain
sensitive information. This issue only affected Ubuntu
Ubuntu
Exim vulnerability
vendor_ubuntu·2024-01-29
CVE-2023-51766 Exim vulnerability
Title: Exim vulnerability
Summary: Exim could be made to bypass an SPF protection mechanism if it received
a specially crafted request.
It was discovered that Exim incorrectly handled certain requests.
A remote attacker could possibly use a published exploitation technique
to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass
of an SPF protection mechanism.
Instructions: In general, a standard system update will make all the necessary changes.
Debian
CVE-2023-51766: exim4 - Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configur...
vendor_debian·2023·CVSS 5.3
CVE-2023-51766 [MEDIUM] CVE-2023-51766: exim4 - Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configur...
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 . but some other popular e-mail servers do not.
Scope: local
bookworm: resolved (fixed in 4.96-15+deb12u4)
bullseye: resolved (fixed in 4.94.2-7+deb11u2)
forky: resolved (fixed in 4.97-3)
sid: resolved (fixed in 4.97-3)
trixie: resolved (fixed in 4.97-3)
OSV
CVE-2023-51766: Exim before 4
osv·2023-12-24·CVSS 5.3
CVE-2023-51766 [MEDIUM] CVE-2023-51766: Exim before 4
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 . but some other popular e-mail servers do not.
GHSA
GHSA-w6ww-869j-cgm6: Exim through 4
ghsa_unreviewed·2023-12-24
CVE-2023-51766 [MEDIUM] CWE-345 GHSA-w6ww-869j-cgm6: Exim through 4
Exim through 4.97 allows SMTP smuggling in certain configurations. Remote attackers can use a published exploitation technique to inject e-mail messages that appear to originate from the Exim server, allowing bypass of an SPF protection mechanism. This occurs because Exim supports . but some other popular e-mail servers do not.
Suricata
ET EXPLOIT Inbound Setup Message from SMTP Smuggling Tool
suricata·2024-01-05
CVE-2023-51764 ET EXPLOIT Inbound Setup Message from SMTP Smuggling Tool
ET EXPLOIT Inbound Setup Message from SMTP Smuggling Tool
Rule: alert smtp $EXTERNAL_NET any -> $HOME_NET any (msg:"ET EXPLOIT Inbound Setup Message from SMTP Smuggling Tool"; flow:established,to_client; content:"From|3a 20|setup|5f|check|40|"; nocase; content:"To|3a 20|"; nocase; distance:0; content:"Subject|3a 20|SETUP|20|CHECK"; nocase; distance:0; content:"Date|3a 20|"; nocase; distance:0; content:"Message|2d|ID|3a 20|"; nocase; distance:0; content:"Your setup seems to be working! You can now proceed with smuggling tests!"; fast_pattern; nocase; distance:0; reference:cve,2023-51764; reference:url,github.com/The-Login/SMTP-Smuggling-Tools/blob/main/smtp_smuggling_scanner.py; reference:cve,2023-51766; reference:cve,2023-51765; classtype:trojan-activity; sid:2049923; rev:1; metadata:atta
Suricata
ET EXPLOIT Inbound Smuggling Message from SMTP Smuggling Tool M2
suricata·2024-01-05
CVE-2023-51764 ET EXPLOIT Inbound Smuggling Message from SMTP Smuggling Tool M2
ET EXPLOIT Inbound Smuggling Message from SMTP Smuggling Tool M2
Rule: alert smtp $EXTERNAL_NET any -> $HOME_NET any (msg:"ET EXPLOIT Inbound Smuggling Message from SMTP Smuggling Tool M2"; flow:established,to_client; content:"From|3a 20|smuggled|40|"; nocase; content:"To|3a 20|"; nocase; distance:0; content:"Subject|3a 20|SMUGGLED|20|EMAIL"; nocase; distance:0; content:"Date|3a 20|"; nocase; distance:0; content:"Message|2d|ID|3a 20|"; nocase; distance:0; content:"SMUGGLING WORKS with"; nocase; distance:0; content:"as|20 22|fake|22 20|end|2d|of|2d|data|20|sequence|21|"; fast_pattern; nocase; distance:0; reference:cve,2023-51764; reference:url,github.com/The-Login/SMTP-Smuggling-Tools/blob/main/smtp_smuggling_scanner.py; reference:cve,2023-51766; reference:cve,2023-51765; classtype:trojan-
Suricata
ET EXPLOIT Inbound Smuggling Message from SMTP Smuggling Tool M1
suricata·2024-01-05
CVE-2023-51764 ET EXPLOIT Inbound Smuggling Message from SMTP Smuggling Tool M1
ET EXPLOIT Inbound Smuggling Message from SMTP Smuggling Tool M1
Rule: alert smtp $EXTERNAL_NET any -> $HOME_NET any (msg:"ET EXPLOIT Inbound Smuggling Message from SMTP Smuggling Tool M1"; flow:established,to_client; content:"From|3a 20|test|40|"; nocase; content:"To|3a 20|"; nocase; distance:0; content:"Subject|3a 20|CHECK|20|EMAIL"; nocase; distance:0; content:"Date|3a 20|"; nocase; distance:0; content:"Message|2d|ID|3a 20|"; nocase; distance:0; content:"TESTING"; nocase; distance:0; content:"as|20 22|fake|22 20|end|2d|of|2d|data|20|sequence|21|"; fast_pattern; nocase; distance:0; reference:cve,2023-51764; reference:url,github.com/The-Login/SMTP-Smuggling-Tools/blob/main/smtp_smuggling_scanner.py; reference:cve,2023-51766; reference:cve,2023-51765; classtype:trojan-activity; sid:204992
No public exploits indexed.
No writeups or analysis indexed.
http://www.openwall.com/lists/oss-security/2023/12/24/1http://www.openwall.com/lists/oss-security/2023/12/25/1http://www.openwall.com/lists/oss-security/2023/12/29/2http://www.openwall.com/lists/oss-security/2024/01/01/1http://www.openwall.com/lists/oss-security/2024/01/01/2http://www.openwall.com/lists/oss-security/2024/01/01/3https://bugs.exim.org/show_bug.cgi?id=3063https://bugzilla.redhat.com/show_bug.cgi?id=2255852https://exim.org/static/doc/security/CVE-2023-51766.txthttps://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.htmlhttps://git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5cahttps://git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766https://lists.debian.org/debian-lts-announce/2024/01/msg00002.htmlhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/https://lwn.net/Articles/956533/https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/https://www.openwall.com/lists/oss-security/2023/12/23/2https://www.youtube.com/watch?v=V8KPV96g1Tohttp://www.openwall.com/lists/oss-security/2023/12/24/1http://www.openwall.com/lists/oss-security/2023/12/25/1http://www.openwall.com/lists/oss-security/2023/12/29/2http://www.openwall.com/lists/oss-security/2024/01/01/1http://www.openwall.com/lists/oss-security/2024/01/01/2http://www.openwall.com/lists/oss-security/2024/01/01/3https://bugs.exim.org/show_bug.cgi?id=3063https://bugzilla.redhat.com/show_bug.cgi?id=2255852https://exim.org/static/doc/security/CVE-2023-51766.txthttps://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.htmlhttps://git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5cahttps://git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766https://lists.debian.org/debian-lts-announce/2024/01/msg00002.htmlhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/https://lists.fedoraproject.org/archives/list/[email protected]/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/https://lists.fedoraproject.org/archives/list/[email protected]/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/https://lwn.net/Articles/956533/https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/https://www.openwall.com/lists/oss-security/2023/12/23/2https://www.youtube.com/watch?v=V8KPV96g1To
2023-12-24
Published