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             AUSCERT External Security Bulletin Redistribution

                               ESB-2010.0201
         KDE Security Advisory: KRunner lock module race condition
                             25 February 2010

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           KDE 4.4.0
Publisher:         KDE
Operating System:  UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Unauthorised Access -- Console/Physical
Resolution:        Patch/Upgrade

Original Bulletin: 
   http://www.kde.org/info/security/advisory-20100217-1.txt

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KDE Security Advisory: KRunner lock module race condition
Original Release Date: 2010-02-17
URL: http://www.kde.org/info/security/advisory-2010-02-17-1.txt

0. References
        oCert: N/A
        CVE: N/A

1. Systems affected:

        KDE 4.4.0 is the only version affected.

2. Overview:

        KRunner lock module race condition:
        The KRunner lock module forks a process to perform password
        validation. This forking process does not properly check whether an
        existing process has already been forked, creating a race condition if
        the Enter key is pressed after a process has been forked but before
        the password has been validated. In this case, multiple processes can
        be forked, causing a socket listener on the parent to point to either
        an incorrect process that has not received the password data,
        resulting in a hang, or in some cases cause the socket notifier to
        point to an already-deleted object, resulting in a crash that brings
        the user to the desktop and circumvents the lock mechanism.

        Note: the locking is actually performed by KRunner, which is part of
        the kdebase module, and not KScreenSaver; even when no screen saver
        is being used an affected system can still be compromised.

3. Impact:

        This is a critical vulnerability that is easily exploited if physical
        access to a machine is granted, and can result in an attacker gaining
        full privileges of the user whose screen is currently locked.

4. Solution:

        Source code patches have been made available which fix these
        vulnerabilities. OS vendors / binary package providers have been
        contacted and in most cases a patched version should already be
        available. Contact your OS vendor / binary package provider for
        information about how to obtain updated binary packages or for
        information about which version of the package contains the patch.

5. Patch:

        Patches for KDE 4.4.0 have been committed to Subversion, and are
        available from websvn.kde.org:
        http://websvn.kde.org/?view=rev&revision=1089241

        A patch may also be obtained directly from the Subversion repository
        (no checkout needed) with the following command:
        svn diff -r 1089240:1089241 \
svn://anonsvn.kde.org/home/kde/branches/KDE/4.4/kdebase/workspace/krunner/lock

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NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members.  As
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NOTE: This is only the original release of the security bulletin.  It may
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        http://www.auscert.org.au/render.html?cid=1980

If you believe that your computer system has been compromised or attacked in 
any way, we encourage you to let us know by completing the secure National IT 
Incident Reporting Form at:

        http://www.auscert.org.au/render.html?it=3192

===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
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