Remote command execution in Exim

1) OS Command Injection

EUVDB-ID: #VU20924

Risk: High

CVSSv3.1: 8.8 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2019-15846

CWE-ID: CWE-78 - Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to execute arbitrary shell commands on the target system.

The vulnerability exists due to incorrect processing of trailing backslash during TLS connection. A remote unauthenticated attacker can send specially crafted command via an established TLS connection and execute arbitrary OS commands on the target system with root privileges.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Exim: 2.10 - 4.92.1

External links

http://exim.org/static/doc/security/CVE-2019-15846.txt
http://www.openwall.com/lists/oss-security/2019/09/06/2
http://seclists.org/bugtraq/2019/Sep/13
http://www.openwall.com/lists/oss-security/2019/09/06/1

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. However, proof of concept for this vulnerability is available.