[NT] Sybase DBCC CHECKVERIFY Buffer Overflow

From: support@securiteam.com
Date: 11/28/02

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Date: 28 Nov 2002 18:07:21 +0200

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      Sybase DBCC CHECKVERIFY Buffer Overflow
    ------------------------------------------------------------------------

    SUMMARY

    The built-in function DBCC CHECKVERIFY contains a buffer overflow that may
    allow an attacker to overwrite the stack and execute arbitrary code under
    the security context of the server. Any valid login in Sybase is able to
    execute this function.

    DETAILS

    Vulnerable systems:
     * Sybase Adaptive Server version 12.0 and 12.5

    Sybase Adaptive Server provides a built-in function called DBCC
    CHECKVERIFY. This function is used to verify the results of the most
    recent run of dbcc checkstorage.

    DBCC CHECKVERIFY accepts a single parameter that is the name of the
    database to check. DBCC CHECKVERIFY does not validate the length of the
    string passed into the first parameter. This buffer overflow may allow an
    attacker to run arbitrary code under the security context of the database.

    Below is an example of overflowing the buffer using the SQL tool isql.exe.

    1> declare @test varchar(16384)
    2> select @test = replicate('A', 16384)
    3> DBCC CHECKVERIFY(@test)
    4> go

    Fix:
    You should apply the following patches:
     * 12.5.0.2 - 11/14/2002
     * 12.0.0.6 ESD#1 - 11/5/2002

    These patches can be downloaded from
    <http://downloads.sybase.com/swd/swx> http://downloads.sybase.com/swd/swx

    ADDITIONAL INFORMATION

    The original advisory can be downloaded from:
     <http://www.appsecinc.com/resources/alerts/sybase/02-0001.html>
    http://www.appsecinc.com/resources/alerts/sybase/02-0001.html

    The information has been provided by <mailto:anewman@appsecinc.com> Aaron
    C. Newman (Application Security, Inc.).

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