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CONECTIVA LINUX SECURITY ANNOUNCEMENT 
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PACKAGE   : vnc
SUMMARY   : Vulnerabilties in cookies and random challenge generations
DATE      : 2003-05-05 17:49:00
ID        : CLA-2003:640
RELEVANT
RELEASES  : 7.0, 8

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DESCRIPTION
 Virtual Network Computing (VNC) is a tool that provides remote
 display viewing/controlling.
 
 This update fixes two vulnerabilities found in VNC that affect the
 versions distributed with Conectiva Linux 7.0 and 8:
 
 - Weak challenge number generation[1]
 VNC uses a challenge-response schema for authentication, but it uses
 the same challenge for multiple connections that are done in an
 interval of one second. An attacker can exploit this vulnerability by
 sniffing the connection and using the same challenge/response of a
 valid conection to gain access without having a valid account in the
 vnc server. This vulnerability was fixed in TightVNC 1.2.6.
 
 The Common Vulnerabilities and Exposures (CVE) project has assigned
 the name CAN-2002-1336 to this issue[2].
 
 - Weak Xcookie generation
 When the VNC server acts as an XServer, it generates a
 MIT-MAGIC-COOKIE[4] to authenticate users. VNC versions up to
 3.3.3r2-21 generate such a cookie in an unsafe manner (not randomly
 enough), allowing attackers to more easily guess it. A remote
 attacker can access the vnc server without having permission to do so
 if it knows the cookie value.
 
 The Common Vulnerabilities and Exposures (CVE) project has assigned
 the name CAN-2002-1511 to this issue[3].


SOLUTION
 All vnc users should upgrade.
 
 
 REFERENCES:
 1.http://marc.theaimsgroup.com/?l=bugtraq&m=102753170201524
 2.http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-1336
 3.http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-1511
 4.http://www-ugrad.cs.colorado.edu/udp/xauth.html


UPDATED PACKAGES
ftp://atualizacoes.conectiva.com.br/7.0/RPMS/vnc-3.3.3-6U70_2cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/7.0/SRPMS/vnc-3.3.3-6U70_2cl.src.rp
ftp://atualizacoes.conectiva.com.br/8/RPMS/vnc-3.3.3r2+tight1.2.2-6U80_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/vnc-java-3.3.3r2+tight1.2.2-6U80_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/RPMS/vnc-server-3.3.3r2+tight1.2.2-6U80_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/8/SRPMS/vnc-3.3.3r2+tight1.2.2-6U80_1cl.src.rpm


ADDITIONAL INSTRUCTIONS
 The apt tool can be used to perform RPM packages upgrades:

 - run:                 apt-get update
 - after that, execute: apt-get upgrade

 Detailed instructions reagarding the use of apt and upgrade examples 
 can be found at http://distro.conectiva.com.br/atualizacoes/#apt?idioma=en

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All packages are signed with Conectiva's GPG key. The key and instructions
on how to import it can be found at 
http://distro.conectiva.com.br/seguranca/chave/?idioma=en
Instructions on how to check the signatures of the RPM packages can be
found at http://distro.conectiva.com.br/seguranca/politica/?idioma=en

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All our advisories and generic update instructions can be viewed at
http://distro.conectiva.com.br/atualizacoes/?idioma=en

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Copyright (c) 2003 Conectiva Inc.
http://www.conectiva.com

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