| Name | CVE-2023-51764 |
| Description | 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. |
| Source | CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DLA-3725-1 |
| Debian Bugs | 1059230 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| postfix (PTS) | buster | 3.4.23-0+deb10u1 | vulnerable |
| buster (security) | 3.4.23-0+deb10u2 | fixed | |
| bullseye | 3.5.24-0+deb11u1 | fixed | |
| bookworm | 3.7.10-0+deb12u1 | fixed | |
| trixie | 3.8.5-1 | fixed | |
| sid | 3.9.0-2 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| postfix | source | buster | 3.4.23-0+deb10u2 | DLA-3725-1 | ||
| postfix | source | bullseye | 3.5.23-0+deb11u1 | |||
| postfix | source | bookworm | 3.7.9-0+deb12u1 | |||
| postfix | source | (unstable) | 3.8.4-1 | 1059230 |
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://lists.debian.org/debian-stable-announce/2023/12/msg00004.html
Short-term Mitigation: smtpd_forbid_unauth_pipelining = yes
Long-term fix with new (optional) feature that is disabled by default:
New setting: smtpd_forbid_bare_newline = yes
https://www.openwall.com/lists/oss-security/2023/12/22/3
Fixes for older releases: https://www.postfix.org/smtp-smuggling.html#back-ports