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Re: Metasploit - CVE-2012-1823 - Snort Sleeping
From: James Lay <jlay () slave-tothe-box net>
Date: Fri, 26 Apr 2013 14:49:45 -0600

On 2013-04-26 14:43, MA Bel wrote:

I found a working exploit (reverse shell) where Snort’s signature
fail to trigger an alert.

In a lab I have 3 physical hosts: one Snort, one with BackTrack, and
one Ubuntu running Metasploitable in VirtualBox. I use Metasploit to
attack the Metasploitable VM, Snort is in passive (non-inline) mode.

I came across CVE-2012-1823 (PHP CGI Argument Injection) which
corresponds to three potential snort signatures: 22097, 22063, 22064.
Metasploit has a nice exploit that will give you a reverse shell. It


SID 22063’s rule attempts to catch the string
“auto_prepend_file” When the Metasploint exploit is launched,
WireShark confirms that the string is indeed sent. I get a reverse
shell. I can list directories, move into them, delete stuff, etc, yet
Snort does not generate an alert. Yes, rules are up to date,
activated, etc. The basics are covered.

I decided to strip off all extra parameters and create a very basic
rule: “content: auto_prepend_file”. No luck catching the exploit.
I used Scapy to send the “auto_prepend_file” string. Snort woke
up. I used Scapy to send the whole string sent by Metasploit (I did a
copy & paste of what I found in Wireshark). That works, Snort wakes

I don’t understand why an http string sent by Scapy generates an
alert whereas the same string sent by Metasploit keeps Snort silent. 
am not event using evasion techniques.

How do I get Snort to catch the exploit? I am worried other rules
won't fire when they should.

Thanks in advance.



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