SMTP smuggling attack in Exim

1) Command Injection

EUVDB-ID: #VU84728

Risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2023-51766

CWE-ID: CWE-77 - Command injection

Exploit availability: No

Description

The vulnerability allows a remote attacker to spoof email messages.

The vulnerability exists due to an error when handling line endings other than <CR><LF>. A remote attacker can spoof contents of email message and bypass SPF protection mechanism.

Mitigation

Install update from vendor's website.

Vulnerable software versions

Exim: 4.00 - 4.97

External links

http://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/
http://exim.org/static/doc/security/CVE-2023-51766.txt
http://bugs.exim.org/show_bug.cgi?id=3063
http://www.openwall.com/lists/oss-security/2023/12/23/2
http://www.openwall.com/lists/oss-security/2023/12/24/1

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.