Imail Web Service Remote DoS Attack v.2



Release Date:

August 17, 2000



Systems Affected:

Ipswitch Imail 6.00 2-1



Description:

The following is a simple DoS we found while working on Retina's CHAM(Common Hacking Attack Methods) HTTP auditing module which should be released within the next two weeks within the new Retina 2.5.



There exists a remote Denial of Service in Ipswitch's Imail web services in IMail 6.0.  The problem arises in incorrect handling of HTTP 1.1 Host header portions of requests.  By using a long Host: header, you can cause a single thread to crash. When this thread crashes, it does not free it's resources, allowing an attacker to repeat this process to use massive amounts of memory

on the server.



Details:

The problem is in the Host: processing.  Sending anywhere over 500 bytes will cause the thread to overwrite it's Base pointer, killing operations on that thread.  Resources are not freed for the thread, however, so this can cause the attacked server to use massive amounts of memory.  After a while, this program will cause serious problems for the server.  Some of the problems we have experienced are: systems stopped responding to mouse

clicks, systems completely freezing etc...



The attack:

 GET / HTTP/1.1

 Host: AAAAAAAA(x500)



The Attack Program:

We have created a sample attack program that can quickly cause massive amounts of memory to be used by the attacked server.



The crashimail.exe example should be called as follows:

 crashimail hostname port numthreads

 The hostname is the host you wish to attack

 the port is a port of the Imail's Web service, Imail defaults to 8181 or 8383  numthreads is the number of concurrent threads to attack with



You can download this sample program and source from:

http://www.eeye.com/html/advisories/threadcrashimail.zip



Vendor Status:

We would like to thank IPSwitch (www.ipswitch.com) for the way they handled this vulnerability in a timely fashion.

A fix for this can be found at, http://www.ipswitch.com/support/patches-upgrades.html#IMail.



For more information about Retina and its CHAM (Common Hacking Attack Methods) technology, visit http://www.eeye.com/retina



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