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Re: Should nmap cause a DoS on cisco routers?
From: Thierry Zoller <Thierry () Zoller lu>
Date: Thu, 1 Jul 2010 11:28:37 +0200

Hi Shang,

If  this  is  possible  you  have  found  a  vulnerability. Any way to
remotely  cause  DoS  with  special  or  harmless  code  is  per  se a

Instead  of  telling  somebody  to not scan with -sV you are better of
reporting the vulnerability (ies)


coc> During my training classes I always tell the -sV switch is
coc> dangerous and known to (sometimes) crash the target.  

coc> Usually a better tool to test open udp ports is unicornscan, but
coc> that doesn't have a switch like -iL. Since you are testing your
coc> own devices and you know the community string, you could insider
coc> to loop through the list of IP's and snmpget a value from the MIB.

coc> Cor

coc> sent from a mobile device 

coc> ----Origineel bericht----
coc> Van: Shang Tsung
coc> Verzonden:  30-06-2010 13:03:32
coc> Onderw.:  Should nmap cause a DoS on cisco routers?

coc> Hello,

coc> Some days ago, I had the task to discover the SNMP version that our 
coc> servers and networking devices use. So I run nmap using the following 
coc> command:

coc> nmap -sU -sV -p 161-162 -iL target_file.txt

coc> This command was supposed to use UDP to probe ports 161 and 162, which
coc> are used for SNMP and SNMP Trap respectively, and return the SNMP 
coc> version.

coc> This "innocent" command caused most networking devices to crash and 
coc> reboot, causing a Denial of Service attack and bringing down the 
coc> network.

coc> Now my question is.. Should this had happened? Can nmap bring the whole
coc> network down from one single machine?

coc> Is this a configuration error of the networking devices?

coc> This is scary...

coc> Shang Tsung


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Thierry Zoller

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