#VU20924 OS Command Injection in Exim - CVE-2019-15846

Vulnerability identifier: #VU20924

Vulnerability risk: High

CVSSv4.0: 8.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Amber]

CVE-ID: CVE-2019-15846

CWE-ID: CWE-78

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
Exim
Server applications / Mail servers

Vendor: Exim

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

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

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Q & A

Can this vulnerability be exploited remotely?

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

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.