BugTraq
Nstxd vulnerability Mar 26 2004 10:27PM
laurent oudot (oudot rstack org)


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Rstack Team (Rstack.org) --- Security Advisory

Advisory Number: RSTACK-20040325

Subject: Nstxd remote DoS-Bug (NULL-pointer-dereference)

Author: Laurent Oudot <oudot (at) rstack (dot) org [email concealed]>

Discovered: ...

Published: March 25, 2004

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Problem description

===================

Nstxd is the server from the Nstx project. Nstx can be used to create

IP trafic over DNS (can be used by blackhats for special Wifi networks

with DNS open for everybody).

Unexpected input may crash the server called nstxd which will at least

result in a DOS due to a NULL-pointer-dereference.

The service nstxd runs as root to bind the UDP port 53.

Vulnerable versions

===================

Tests were done with the latest version : nstx-1.1-beta3

http://debmail.dereference.de/nstx/nstx-1.1-beta3.tgz

Vendor status

=============

The Nstx team quickly solved this bug.

A new release is available : nstx-1.1-beta4.

From the ChangeLog :

1.1-beta4: sky

2004/03/26

* Fixed a remote DoS-Bug (NULL-pointer-dereference)

Solutions

=========

* Upgrade your Nstx version at :

http://debmail.dereference.de/nstx/nstx-1.1-beta4.tgz

* Workaround: Containment (chroot, jail...) and low level security

solutions (grsecurity, systrace...) should be use to improve

the security of such a server.

Example

=======

** On the server (assume the IP is 192.168.1.34 for this example):

nstx-1.1-beta3# ./nstxd tun.mydomain.com

** On a remote "evil" client:

remote-hacker$ perl -e '{ print "A" x 500 }' | nc -u 192.168.1.34 53

This will segfault the server.

It might be dangerous as nstxd needs root priviledges (bind port 53).

No exploit to get a remote shell has been reported (just a DOS).

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