Remote code execution in fail2ban

1) Code Injection

EUVDB-ID: #VU55278

Risk: High

CVSSv3.1: 8.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-32749

CWE-ID: CWE-94 - Improper Control of Generation of Code ('Code Injection')

Exploit availability: No

Description

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

The vulnerability exists due to improper input validation in the mailing action mail-whois. A remote attacker can send a specially crafted request and execute arbitrary code on the target system.

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

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Fail2ban: 0.9.0 - 0.11.2

External links

http://github.com/fail2ban/fail2ban/commit/410a6ce5c80dd981c22752da034f2529b5eee844
http://github.com/fail2ban/fail2ban/commit/2ed414ed09b3bb4c478abc9366a1ff22024a33c9
http://github.com/fail2ban/fail2ban/security/advisories/GHSA-m985-3f3v-cwmm

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.