CVE-2023-51764
Published: 24 December 2023
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.
Notes
Author | Note |
---|---|
mdeslaur | We will not be releasing updates for Lunar which is EoL on 2024-01-25 |
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
Priority
Status
Package | Release | Status |
---|---|---|
postfix Launchpad, Ubuntu, Debian |
bionic |
Released
(3.3.0-1ubuntu0.4+esm3)
Available with Ubuntu Pro or Ubuntu Pro (Infra-only) |
focal |
Released
(3.4.13-0ubuntu1.4)
|
|
jammy |
Released
(3.6.4-1ubuntu1.3)
|
|
lunar |
Ignored
(end of life)
|
|
mantic |
Released
(3.8.1-2ubuntu0.2)
|
|
trusty |
Released
(2.11.0-1ubuntu1.2+esm3)
Available with Ubuntu Pro or Ubuntu Pro (Infra-only) |
|
upstream |
Released
(3.8.4-1)
|
|
xenial |
Released
(3.1.0-3ubuntu0.4+esm3)
Available with Ubuntu Pro or Ubuntu Pro (Infra-only) |
Severity score breakdown
Parameter | Value |
---|---|
Base score | 5.3 |
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 |
References
- https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/
- https://www.openwall.com/lists/oss-security/2023/12/21/6
- https://www.postfix.org/smtp-smuggling.html
- https://www.mail-archive.com/postfix-users@postfix.org/msg100901.html
- https://www.openwall.com/lists/oss-security/2023/12/22/3
- https://ubuntu.com/security/notices/USN-6591-1
- https://ubuntu.com/security/notices/USN-6591-2
- https://www.cve.org/CVERecord?id=CVE-2023-51764
- NVD
- Launchpad
- Debian