CVE-2023-51764
moderate-risk
Published 2023-12-24
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.
Do I need to act?
!
27.1% chance of exploitation in next 30 days
EPSS score — higher than 73% of all CVEs
-
Not on CISA KEV list
No confirmed active exploitation reported to CISA
?
Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
5
CVSS 5.3/10
Medium
NETWORK
/ LOW complexity
Affected Products (5)
Affected Vendors
References (36)
Third Party Advisory
https://access.redhat.com/security/cve/CVE-2023-51764
Issue Tracking
https://bugzilla.redhat.com/show_bug.cgi?id=2255563
Technical Description
https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html
Technical Description
https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/
and 16 more references
48
/ 100
moderate-risk
Severity
21/34 · High
Exploitability
15/34 · Moderate
Exposure
12/34 · Low