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CVE-2023-51764

Publication date 24 December 2023

Last updated 24 July 2024

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

5.3 · Medium

Score breakdown

Postfix through 3.8.5 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehlo_keywords=chunking (or certain other options that exist in recent versions). 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 Postfix supports <LF>.<CR><LF> but some other popular e-mail servers do not. To prevent attack variants (by always disallowing <LF> without <CR>), a different solution is required, such as the smtpd_forbid_bare_newline=yes option with a Postfix minimum version of 3.5.23, 3.6.13, 3.7.9, 3.8.4, or 3.9.

Read the notes from the security team

Mitigation

Patched versions of Postfix before 3.9 require the below configs for the fix to apply: smtpd_forbid_bare_newline = normalize smtpd_forbid_bare_newline_exclusions = $mynetworks

Status

Package Ubuntu Release Status
postfix 23.10 mantic
Fixed 3.8.1-2ubuntu0.2
23.04 lunar Ignored end of life
22.04 LTS jammy
Fixed 3.6.4-1ubuntu1.3
20.04 LTS focal
Fixed 3.4.13-0ubuntu1.4
18.04 LTS bionic
16.04 LTS xenial
14.04 LTS trusty

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Notes

mdeslaur

We will not be releasing updates for Lunar which is EoL on 2024-01-25

Severity score breakdown

Parameter Value
Base score 5.3 · Medium
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact Low
Availability impact None
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N