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                   Red Hat, Inc. Red Hat Security Advisory

Synopsis:          Updated VNC packages fix replay and cookie vulnerabilities
Advisory ID:       RHSA-2003:041-12
Issue date:        2003-02-07
Updated on:        2003-02-20
Product:           Red Hat Linux
Keywords:          vnc challenge replay cookie mkcookie
Cross references:  
Obsoletes:         
CVE Names:         CAN-2002-1336 CAN-2002-1511
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1. Topic:

Updated VNC packages are available to fix a challenge replay vulnerability
and a weak cookie vulnerability.

2. Relevant releases/architectures:

Red Hat Linux 7.0 - i386
Red Hat Linux 7.1 - i386
Red Hat Linux 7.2 - i386
Red Hat Linux 7.3 - i386
Red Hat Linux 8.0 - i386

3. Problem description:

VNC is a tool for providing a remote graphical user interface.  Two
vulnerabilities have been found in versions of VNC shipped by Red Hat.

The VNC server acts as an X server, but the script for starting it
generates an MIT X cookie (which is used for X authentication) without
using a strong enough random number generator.  This could allow an
attacker to be able to more easily guess the authentication cookie.

The VNC DES authentication scheme is implemented using a challenge-response
architecture, producing a random and different challenge for each
authentication attempt. A bug in the function for generating the random
challenge caused the random seed to get reset to the current time on every
authentication attempt. Therefore, two authentication attempts within the
same second could receive the same challenge.  An eavesdropper could
exploit this vulnerability by replaying the response, thereby gaining
authentication.

All users of VNC are advised to upgrade to these erratum packages, which
contain patches to correct these issues.

Note that when using VNC on an untrusted network, always make sure to
tunnel it through a secure authenticated protocol such as SSH.

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade.  Only those
RPMs which are currently installed will be updated.  Those RPMs which are
not installed but included in the list will not be updated.  Note that you
can also use wildcards (*.rpm) if your current directory *only* contains the
desired RPMs.

Please note that this update is also available via Red Hat Network.  Many
people find this an easier way to apply updates.  To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

5. Bug IDs fixed  (  for more info):

78828 - Upgrade to tightVNC 1.2.7 from 1.2.2

6. RPMs required:

Red Hat Linux 7.0:

SRPMS: 
 

i386: 
  
  
 

Red Hat Linux 7.1:

SRPMS: 
 

i386: 
  
  
 

Red Hat Linux 7.2:

SRPMS: 
 

i386: 
  
  
 

Red Hat Linux 7.3:

SRPMS: 
 

i386: 
  
  
 

Red Hat Linux 8.0:

SRPMS: 
 

i386: 
  
  
 



7. Verification:

MD5 sum                          Package Name
--------------------------------------------------------------------------
9238c1864c7571432c232b35d4047cbd 7.0/en/os/SRPMS/vnc-3.3.3r2-18.6.src.rpm
c159b4fa8ac650a799e64acbebb3934e 7.0/en/os/i386/vnc-3.3.3r2-18.6.i386.rpm
7087a97e858bd5d38bccb4e69ce2ebdc 7.0/en/os/i386/vnc-doc-3.3.3r2-18.6.i386.rpm
678cbceba744439bca85bb3d01279e59 7.0/en/os/i386/vnc-server-3.3.3r2-18.6.i386.rpm
9238c1864c7571432c232b35d4047cbd 7.1/en/os/SRPMS/vnc-3.3.3r2-18.6.src.rpm
c159b4fa8ac650a799e64acbebb3934e 7.1/en/os/i386/vnc-3.3.3r2-18.6.i386.rpm
7087a97e858bd5d38bccb4e69ce2ebdc 7.1/en/os/i386/vnc-doc-3.3.3r2-18.6.i386.rpm
678cbceba744439bca85bb3d01279e59 7.1/en/os/i386/vnc-server-3.3.3r2-18.6.i386.rpm
9238c1864c7571432c232b35d4047cbd 7.2/en/os/SRPMS/vnc-3.3.3r2-18.6.src.rpm
c159b4fa8ac650a799e64acbebb3934e 7.2/en/os/i386/vnc-3.3.3r2-18.6.i386.rpm
7087a97e858bd5d38bccb4e69ce2ebdc 7.2/en/os/i386/vnc-doc-3.3.3r2-18.6.i386.rpm
678cbceba744439bca85bb3d01279e59 7.2/en/os/i386/vnc-server-3.3.3r2-18.6.i386.rpm
10bbe07038a2a122affc6c5583b83c11 7.3/en/os/SRPMS/vnc-3.3.3r2-28.2.src.rpm
535f8e6e8b531efafc3906a09a7be81e 7.3/en/os/i386/vnc-3.3.3r2-28.2.i386.rpm
cdb33d3b5367de1afe34d3b758096aa9 7.3/en/os/i386/vnc-doc-3.3.3r2-28.2.i386.rpm
40bc575df1a4360d14e0624013e89ecf 7.3/en/os/i386/vnc-server-3.3.3r2-28.2.i386.rpm
7cf3f738c2277cdcece3076c8c629e6e 8.0/en/os/SRPMS/vnc-3.3.3r2-39.2.src.rpm
6b20a3a761015ca503128cea711605a4 8.0/en/os/i386/vnc-3.3.3r2-39.2.i386.rpm
db2ca9e3207bb536c80f3cc360f594c6 8.0/en/os/i386/vnc-doc-3.3.3r2-39.2.i386.rpm
900346576f15c15591e67f4284b4beb0 8.0/en/os/i386/vnc-server-3.3.3r2-39.2.i386.rpm


These packages are GPG signed by Red Hat, Inc. for security.  Our key
is available at  About

You can verify each package with the following command:
    
    rpm --checksig -v 

If you only wish to verify that each package has not been corrupted or
tampered with, examine only the md5sum with the following command:
    
    md5sum 


8. References:
 
http://marc.theaimsgroup.com/?l=bugtraq&m=102753170201524 
CVE -CVE-2002-1336 
CVE -CVE-2002-1511

9. Contact:

The Red Hat security contact is <security@RedHat.com>.  More contact
details at  All Red Hat products

Copyright 2003 Red Hat, Inc.