Vulnerability in Postfix
CVE-2023-51764
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.026 (85.0th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 85th percentile — 85.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.026 · newest: 0.026 · change: 0.000
Affected products
- Postfix
- Fedoraproject Fedora — versions 38, 39
- Red Hat Enterprise Linux — versions 8.0, 9.0
Weakness classification (CWE)
Public proof-of-concept exploits
References
- www.postfix.org/smtp-smuggling.html (Exploit, Mitigation, Vendor Advisory)
- sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/ (Technical Description, Third Party Advisory)
- www.openwall.com/lists/oss-security/2023/12/24/1 (mailing-list, Mailing List, Third Party Advisory)
- www.openwall.com/lists/oss-security/2023/12/25/1 (mailing-list, Mailing List, Third Party Advisory)
- bugzilla.redhat.com/show_bug.cgi (Third Party Advisory, Issue Tracking)
- access.redhat.com/security/cve/CVE-2023-51764 (Third Party Advisory)
- fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html (Technical Description)
- github.com/eeenvik1/CVE-2023-51764 (Exploit, Third Party Advisory)
- github.com/duy-31/CVE-2023-51764 (Exploit, Third Party Advisory)
- www.youtube.com/watch (Exploit)
Frequently asked questions
- What is CVE-2023-51764?
- CVE-2023-51764 is a medium-severity vulnerability in Postfix, classified under Insufficient Verification of Data Authenticity. CVSS score: 5.3/10. Published 2023-12-24.
- How severe is CVE-2023-51764?
- Medium severity. CVSS v3 base score is 5.3 out of 10.
- Is CVE-2023-51764 known to be exploited?
- 8 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.