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CVE-2023-51766

Published: Dec 24, 2023Updated: Nov 4, 2025 Sources: CVE List NVD BDUCWE-345
NVD MITRE
5.3CVSSMEDIUM
EPSS Score
1.1%
Top 39.5%
CISA KEV
Not in KEV
Exploits
1 Known
Remediation
Patch Available
Am I actually vulnerable?1 Nuclei template available — see how to check your systems. How to verify

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 Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-345

Affected Products

n/an/a
РЕД ОСООО «Ред Софт»
On-premOS
Operating Systems / linux-distro
Astra Linux Special EditionООО «РусБИТех-Астра»
On-premOS
Operating Systems / linux-distro
Astra Linux Common EditionООО «РусБИТех-Астра»
On-premOS
Operating Systems / linux-distro
eximGNU General Public LicenseOSS Libraries
ооо «ред софт»commercialRUOperating Systemsaka red soft
ооо «русбитех-астра»commercialRUOperating Systemsaka rusbitech-astra
gnu general public licenseoss-projectUSOSS Librariesaka gnu gpl, gpl
and 5 more affected products View all →

Attack Graph

Products CVE Techniques Tactics

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Exploitability

1 exploit source identified

Exploit details including PoC links, Metasploit modules, and scanner templates are available after registration.

View exploit details
Official Patch Available
Workaround Available

MITRE ATT&CK

1 technique
Collection
View detailed technique mapping

References

https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/
sec-consult.com
https://exim.org/static/doc/security/CVE-2023-51766.txt
exim.org
https://bugs.exim.org/show_bug.cgi?id=3063
bugs.exim.org
and 28 more references View all →

Timeline

Published
Dec 24, 2023
Last Updated
Nov 4, 2025

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