HTTP Request Smuggling Affecting sendmail-cf package, versions <0:8.18.2-2.amzn2023.0.1


Severity

Recommended
0.0
medium
0
10

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
1.07% (61st percentile)

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  • Snyk IDSNYK-AMZN2023-SENDMAILCF-17290776
  • published10 Jun 2026
  • disclosed24 Dec 2023

Introduced: 24 Dec 2023

CVE-2023-51765  (opens in a new tab)
CWE-444  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 sendmail-cf to version 0:8.18.2-2.amzn2023.0.1 or higher.
This issue was patched in ALAS2023-2026-1818.

NVD Description

Note: Versions mentioned in the description apply only to the upstream sendmail-cf package and not the sendmail-cf package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

sendmail through 8.17.2 allows SMTP smuggling in certain 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 sendmail supports <LF>.<CR><LF> but some other popular e-mail servers do not. This is resolved in 8.18 and later versions with 'o' in srv_features.

CVSS Base Scores

version 3.1