IIS 4.0 remote DoS (MS99-029)

[n-miwa () LAC CO JP (Nobuo Miwa)]

Hi,

I found a kind of DoS attack against IIS 4.0 on NT SP4 & SP5.
I reported it to MS and they've provided HotFix for this.

Problem Description
-------------------
Simple play. I sent lots of "Host:aaaaa...aa" to IIS like...

  GET / HTTP/1.1
  Host: aaaaaaaaaaaaaaaaaaaaaaa....(200 bytes)
  Host: aaaaaaaaaaaaaaaaaaaaaaa....(200 bytes)
  ...10,000 lines
  Host: aaaaaaaaaaaaaaaaaaaaaaa....(200 bytes)

I sent twice above request sets. Then somehow victim IIS got
memory leak after these requests. Of course, it can not
respond any request any more.
If you try this, you should see memory increase through
performance monitor. You would see memory increase even after
those requests finished already. It will stop when you got
shortage of virtual memory.
After that, you might not be able to restart web service and
you would restart computer.
I tried this against Japanese and English version of Windows NT.

Fix Information
---------------
MS announced in their Security Bulletin as following :
http://www.microsoft.com/security/bulletins/MS99-029faq.asp

Additional information
----------------------
You'll realize someone release exploit code of this thing.
It's easy to make it by using perl or another scripts.

<Nobuo Miwa> n-miwa () lac co jp       ( @ @ ) http://www.lac.co.jp/security
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