CVE-2023-51766

Public Exploit

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.

Category

5.3
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 3.21% Top 15%
Vendor Advisory fedoraproject.org Vendor Advisory fedoraproject.org Vendor Advisory exim.org Vendor Advisory github.com
Affected: n/a n/a
Published at:
Updated at:

References

Link Tags
https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/ third party advisory technical description
https://exim.org/static/doc/security/CVE-2023-51766.txt broken link
https://bugs.exim.org/show_bug.cgi?id=3063 vendor advisory issue tracking
https://www.openwall.com/lists/oss-security/2023/12/23/2 mailing list third party advisory issue tracking
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://git.exim.org/exim.git/commit/5bb786d5ad568a88d50d15452aacc8404047e5ca patch
https://git.exim.org/exim.git/commit/cf1376206284f2a4f11e32d931d4aade34c206c5 patch
https://bugzilla.redhat.com/show_bug.cgi?id=2255852 third party advisory issue tracking
https://fahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.html technical description
http://www.openwall.com/lists/oss-security/2023/12/29/2 mailing list mitigation third party advisory
https://github.com/Exim/exim/blob/master/doc/doc-txt/cve-2023-51766 mitigation vendor advisory
http://www.openwall.com/lists/oss-security/2024/01/01/1 third party advisory mailing list
http://www.openwall.com/lists/oss-security/2024/01/01/2 third party advisory mailing list
http://www.openwall.com/lists/oss-security/2024/01/01/3 third party advisory mailing list
https://www.youtube.com/watch?v=V8KPV96g1To exploit
https://lists.debian.org/debian-lts-announce/2024/01/msg00002.html third party advisory mailing list
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QPDWHJPABVJCXDSNELSSVTIVAJU2MDUQ/ vendor advisory mailing list third party advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ORN7OKEQPPBKUHYRQ6LR5PSNBQVDHAWB/ vendor advisory mailing list third party advisory
https://lwn.net/Articles/956533/ third party advisory

Frequently Asked Questions

What is the severity of CVE-2023-51766?
CVE-2023-51766 has been scored as a medium severity vulnerability.
How to fix CVE-2023-51766?
To fix CVE-2023-51766, 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-2023-51766 being actively exploited in the wild?
It is possible that CVE-2023-51766 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~3% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
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