ksrt.accelerated-x.bof.txt

`Date: Sat, 26 Jun 1999 15:40:54 -0400  
From: "KSR[T] Contact Account" <[email protected]>  
To: [email protected]  
Subject: KSR[T] #011: Accelerated-X  
  
KSR[T] Advisory #011  
Date: June 25, 1999  
ID #: accelx-bo-011  
  
Affected Program: Xi Graphics, Inc.'s Accelerated-X Server 4.x, 5.x  
(and possibly earlier versions).  
  
Author: Jordan Ritter <[email protected]>  
  
Operating System(s): UNIX (Linux, FreeBSD, Solaris/x86, SCO)  
  
Summary: Local users can gain administrative privileges by  
exploiting multiple buffer overflows (stack  
overwrites) in the Accelerated-X X server.  
  
Problem Description: Accelerated-X Server is a commercial X server  
available from http://www.xig.com/. By default,  
the X server is installed setuid root so that  
when it is executed by a user it still retains enough  
privilege to load drivers, manipulate the  
display, and log information.  
  
However, due to insufficient bounds checking on  
command-line parameters, an attacker can overflow  
the X server by specifying a 48 byte display string,  
or through a long string passed into the -query  
command line parameter.  
  
Compromise: Local users that can execute the Accelerated-X  
Xserver can obtain root privileges.  
  
Notes: We would like to thank Chris Evans for pointing  
out the -query buffer overflow as well as additional  
security holes relating to command line parameters.  
  
Patch/Fix: For AccelX 5.x: XiG has made a patch available for  
5.0.1 which corrects these and other potential  
command line interface security holes. Users  
running 5.0.0 have to apply the 5.0.1 patch prior  
to applying the 5.0.2 patch. The patch is  
available at ftp://ftp.xig.com/pub/updates.  
  
For AccelX 4.x: Patch will be made available shortly.  
An interim solution is to use an X server wrapper,  
or to limit access to the Xaccel binary via a  
special group.  
  
The upcoming release of Maximum CDE 2.1 comes with  
the 5.0.2 X Server, and is not vulnerable to these  
attacks.  
  
`