OSEC

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Bugtraq archives for 2nd quarter (Apr-Jun) 1999: Re: NT/Exceed D.O.S.

Re: NT/Exceed D.O.S.

Matt Wilbur (mattPHOTON.COM)
Wed, 28 Apr 1999 13:57:51 -0700 

Exceed (an X server, not an X emulator) version 6.0.1.0 on NT appears to
have fixed this problem, somewhat...

Telnetting to port 6000 locks the server up for 20-30 seconds, but it
recovers eventually.  Not surprisingly, using netcat has the same effect...
although, contrary to Chris's findings with Exceed 5, I didn't need to send
any garbage characters, the connection alone did the job.  Also, it works
from any host, not just the one the xdm session had been initiated with,
regardless of host access settings in Xconfig, Exceeds "configuration" tool.


I'd still consider this DoS-bait, when you imagine a one-liner to
continuously connect to port 6000 of your favorite Exceed user's machine.

Matt Wilbur

[snip]
>
> This is regarding Hummingbird's Exceed X emulator v5 (and possibly v6)
> running on Windows NT.  I haven't tested Win95/98.
>
> The Exceed X server allows inbound TCP connections on port
> 6000 from the XDM> host.  If someone uses telnet from the XDM host to
connect to
> a PC running Exceed on port 6000 and enters any garbage text, the X server

> will hang and the Exceed session is frozen for good.
>
> I have notified Hummingbird via their tech support web site
> but have not received a response yet.
>
> Chris LaFournaise
> cjlafournaiseescocorp.com
>