Gentoo: Screen UTF-8 character handling vulnerability
Posted by Benjamin D. Thomas   
Gentoo Screen contains an error in its UTF-8 character handling code that would allow a remote Denial of Service or possibly the remote execution of arbitrary code.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Gentoo Linux Security Advisory                           GLSA 200611-01
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                                             http://security.gentoo.org/
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

   Severity: High
      Title: Screen: UTF-8 character handling vulnerability
       Date: November 03, 2006
       Bugs: #152770
         ID: 200611-01

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Synopsis
=3D=3D=3D=3D=3D=3D=3D=3D

Screen contains an error in its UTF-8 character handling code that
would allow a remote Denial of Service or possibly the remote execution
of arbitrary code.

Background
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

Screen is a full-screen window manager that multiplexes a physical
terminal between several processes, typically interactive shells.

Affected packages
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

     -------------------------------------------------------------------
      Package          /  Vulnerable  /                      Unaffected
     -------------------------------------------------------------------
   1  app-misc/screen       < 4.0.3                            >=3D 4.0.3=


Description
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

cstone and Richard Felker discovered a flaw in Screen's UTF-8 combining
character handling.

Impact
=3D=3D=3D=3D=3D=3D

The vulnerability can be exploited by writing a special string of
characters to a Screen window. A remote attacker could cause a Denial
of Service or possibly execute arbitrary code with the privileges of
the user running Screen through a program being run inside a Screen
session, such as an IRC client or a mail client.

Workaround
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

There is no known workaround at this time.

Resolution
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

All Screen users should upgrade to the latest version:

     # emerge --sync
     # emerge --ask --oneshot --verbose ">=3Dapp-misc/screen-4.0.3"

References
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

   [ 1 ] CVE-2006-4573
         http://cve.mitre.org/cgi-bin/cvename.cgi?name=3DCVE-2006-4573

Availability
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

   http://security.gentoo.org/glsa/glsa-200611-01.xml

Concerns?
=3D=3D=3D=3D=3D=3D=3D=3D=3D

Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users machines is of utmost
importance to us. Any security concerns should be addressed to
security@gentoo.org or alternatively, you may file a bug at
http://bugs.gentoo.org.

License
=3D=3D=3D=3D=3D=3D=3D

Copyright 2006 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

http://creativecommons.org/licenses/by-sa/2.5