Vulnerability in Exim
CVE-2023-51766
Exim before 4.97.1 allows SMTP smuggling in certain PIPELINING/CHUNKING configurations. 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 Exim supports <LF>.<CR><LF> but some other popular e-mail servers do not.
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: 0.011 (64.4th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 64th percentile — 64.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: 0.000
Affected products
- Exim
- Debian Linux — versions 10.0
- Fedoraproject Extra Packages For Enterprise Linux — versions 7.0, 8.0, 9.0
- Fedoraproject Fedora — versions 38, 39
Weakness classification (CWE)
Public proof-of-concept exploits
References
- sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/ (Technical Description, Third Party Advisory)
- exim.org/static/doc/security/CVE-2023-51766.txt (Broken Link)
- bugs.exim.org/show_bug.cgi (Issue Tracking, Vendor Advisory)
- www.openwall.com/lists/oss-security/2023/12/23/2 (Mailing List, Third Party Advisory, Issue Tracking)
- 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)
- git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5ca (Patch)
- git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5 (Patch)
- bugzilla.redhat.com/show_bug.cgi (Third Party Advisory, Issue Tracking)
- fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html (Technical Description)
Frequently asked questions
- What is CVE-2023-51766?
- CVE-2023-51766 is a medium-severity vulnerability in Exim, classified under Insufficient Verification of Data Authenticity. CVSS score: 5.3/10. Published 2023-12-24.
- How severe is CVE-2023-51766?
- Medium severity. CVSS v3 base score is 5.3 out of 10.
- Is CVE-2023-51766 known to be exploited?
- 7 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.