CVE-2023-51766
MEDIUMCVSS 5.3/10EPSS 1.07%
Last modified
CVE-2023-51766 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. 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. EPSS estimates a 1.07% chance of exploitation in the next 30 days.
Description
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Exim | Exim | < 4.97.1 |
| Fedoraproject | Extra Packages For Enterprise Linux | 7.0 |
| Fedoraproject | Extra Packages For Enterprise Linux | 8.0 |
| Fedoraproject | Extra Packages For Enterprise Linux | 9.0 |
| Fedoraproject | Fedora | 38 |
| Fedoraproject | Fedora | 39 |
| Debian | Debian Linux | 10.0 |
References
- http://www.openwall.com/lists/oss-security/2023/12/24/1Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/12/25/1Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/12/29/2Mailing List, Mitigation, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2024/01/01/1Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2024/01/01/2Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2024/01/01/3Mailing List, Third Party Advisory
- https://bugs.exim.org/show_bug.cgi?id=3063Issue Tracking, Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2255852Issue Tracking, Third Party Advisory
- https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.htmlTechnical Description
- https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766Mitigation, Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2024/01/msg00002.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/Mailing List, Third Party Advisory
- https://lwn.net/Articles/956533/Third Party Advisory
- https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/Technical Description, Third Party Advisory
- https://www.openwall.com/lists/oss-security/2023/12/23/2Issue Tracking, Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/12/24/1Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/12/25/1Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2023/12/29/2Mailing List, Mitigation, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2024/01/01/1Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2024/01/01/2Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2024/01/01/3Mailing List, Third Party Advisory
- https://bugs.exim.org/show_bug.cgi?id=3063Issue Tracking, Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2255852Issue Tracking, Third Party Advisory
- https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.htmlTechnical Description
- https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766Mitigation, Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2024/01/msg00002.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/Mailing List, Third Party Advisory
- https://lwn.net/Articles/956533/Third Party Advisory
- https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/Technical Description, Third Party Advisory
- https://www.openwall.com/lists/oss-security/2023/12/23/2Issue Tracking, Mailing List, Third Party Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is 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.
How severe is CVE-2023-51766?
CVE-2023-51766 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 1.07% probability of exploitation in the next 30 days.
How do I fix CVE-2023-51766?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
Are you affected by CVE-2023-51766?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST