XML External Entity injection in pfsense

1) XML External Entity injection

EUVDB-ID: #VU21375

Risk: Medium

CVSSv3.1: 7.1 [CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H/E:P/RL:U/RC:C]

CVE-ID: CVE-2019-16701

CWE-ID: CWE-611 - Improper Restriction of XML External Entity Reference ('XXE')

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to gain access to sensitive information.

The vulnerability exists due to insufficient validation of user-supplied XML input. A remote attacker can pass a specially crafted methodCall XML document to the affected application and execute arbitrary OS commands on the system via the pfsense.exec_php call containing shell metacharacters in a parameter value.

Successful exploitation of the vulnerability may allow an attacker to view contents of arbitrary file on the server or perform network scanning of internal and external infrastructure.

Mitigation

Cybersecurity Help is currently unaware of any official solution to address this vulnerability.

Vulnerable software versions

pfsense: 2.3.1_1 - 2.4.4_3

External links

http://packetstormsecurity.com/files/154587/pfSense-2.3.4-2.4.4-p3-Remote-Code-Injection.html
http://github.com/pfsense/pfsense/commits/master
http://hackernews.blog/pfsense-2-3-4-2-4-4-p3-remote-code-injection/#more

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.