CVE-2023-51764

Public Exploit

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.

Category

5.3
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 23.08% Top 5%
Vendor Advisory fedoraproject.org Vendor Advisory fedoraproject.org Vendor Advisory postfix.org
Affected: n/a n/a
Published at:
Updated at:

References

Link Tags
https://www.postfix.org/smtp-smuggling.html vendor advisory mitigation exploit
https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/ third party advisory technical description
http://www.openwall.com/lists/oss-security/2023/12/24/1 third party advisory mailing list
http://www.openwall.com/lists/oss-security/2023/12/25/1 third party advisory mailing list
https://bugzilla.redhat.com/show_bug.cgi?id=2255563 third party advisory issue tracking
https://access.redhat.com/security/cve/CVE-2023-51764 third party advisory
https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html technical description
https://github.com/eeenvik1/CVE-2023-51764 third party advisory exploit
https://github.com/duy-31/CVE-2023-51764 third party advisory exploit
https://www.youtube.com/watch?v=V8KPV96g1To exploit
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRLF5SOS7TP5N7FQSEK2NFNB44ISVTZC/ vendor advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/ vendor advisory
https://lwn.net/Articles/956533/
https://www.openwall.com/lists/oss-security/2024/01/22/1
https://www.postfix.org/announcements/postfix-3.8.5.html
https://lists.debian.org/debian-lts-announce/2024/01/msg00020.html mailing list
http://www.openwall.com/lists/oss-security/2024/05/09/3 mailing list

Frequently Asked Questions

What is the severity of CVE-2023-51764?
CVE-2023-51764 has been scored as a medium severity vulnerability.
How to fix CVE-2023-51764?
To fix CVE-2023-51764, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2023-51764 being actively exploited in the wild?
It is possible that CVE-2023-51764 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~23% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
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