CVE & CISA-KEV Catalog

CVE-2023-51766

MEDIUM
5.3
CVSS v3
NVD

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.

CWE-345

How to fix

Remediation Available
exim4Debian
Fixed in:4.94.2-7+deb11u2CVE-2023-51766
Fixed in:4.96-15+deb12u4CVE-2023-51766
Fixed in:4.97-3CVE-2023-51766
Fixed in:4.97-3CVE-2023-51766
exim4Ubuntu
Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1
Fixed in:4.86.2-2ubuntu2.6+esm6USN-6611-1
Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1
Fixed in:4.90.1-1ubuntu1.10+esm3USN-6611-1
Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1
Fixed in:4.93-13ubuntu1.10USN-6611-1
Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1
Fixed in:4.95-4ubuntu2.5USN-6611-1
Fixed in:4.96-17ubuntu2.2USN-6611-1
exim4-baseUbuntu
Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1
Fixed in:4.86.2-2ubuntu2.6+esm6USN-6611-1
Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1
Fixed in:4.90.1-1ubuntu1.10+esm3USN-6611-1
Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1
Fixed in:4.93-13ubuntu1.10USN-6611-1
Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1
Fixed in:4.95-4ubuntu2.5USN-6611-1
Fixed in:4.96-17ubuntu2.2USN-6611-1
exim4-daemon-heavyUbuntu
Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1
Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1
Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1
Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1
exim4-daemon-lightUbuntu
Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1
Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1
Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1
Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1
exim4-devUbuntu
Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1
Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1
Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1
Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1
eximon4Ubuntu
Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1
Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1
Fixed in:4.86.2-2ubuntu2.6+esm6USN-6611-1
Fixed in:4.90.1-1ubuntu1.10+esm3USN-6611-1
Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1
Fixed in:4.93-13ubuntu1.10USN-6611-1
Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1
Fixed in:4.95-4ubuntu2.5USN-6611-1
Fixed in:4.96-17ubuntu2.2USN-6611-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged

Impact

ConfidentialityNone
IntegrityLow
AvailabilityNone

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

Exploit Intelligence

1.07%probability of exploitation in 30 days
61stpercentile

Moderate risk: more likely to be exploited than 61% of all known CVEs.

References

Exploit1
Vendor Advisory2
Mitigation1
Technical Description1
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-04.