[NT] Microsoft Windows Task Scheduler '.job' Stack Overflow
From: SecuriTeam (support_at_securiteam.com)
Date: 07/14/04
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To: list@securiteam.com Date: 14 Jul 2004 18:31:29 +0200
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Microsoft Windows Task Scheduler '.job' Stack Overflow
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SUMMARY
The Microsoft Windows operating system provides a service which is
designed to run a particular application at a given time or date - the
Task Scheduler. When a new task is added through the control panel
application, a '.job' file containing this information is created and
stored in the 'Tasks' folder in the Windows directory.
It has been found that it is possible to create a specially crafted '.job'
file which could allow local or remote code execution using a number of
different applications as the attack vectors.
DETAILS
By crafting a '.job' file which contains overly long parameters, stack
based buffers can be overflowed, resulting in critical information,
including a saved return address or a structured exception handler
structure being completely overwritten, allowing an attacker to direct the
code execution flow to an address of their choosing. If the file contains
arbitrary executable code, the process can be forced to execute this
allowing, in worst cases, complete control over the target system.
The actual vulnerability arises from a lack of boundary checking performed
when copying the information out of memory containing the contents of the
file into the stack-based buffers.
In some circumstances the overflow is triggered automatically when viewing
the directory that contains the job file in an explorer window due to the
fact that 'shell32.dll' will detect the '.job' file extension, and load
'mstask.dll' allowing the module to examine the file, which is when the
overflow occurs.
Due to the fact that the overflow is triggered by a module loaded within
the process space of another running executable, any code which would be
executed by exploiting this flaw will be run with the privileges of the
user running that application, in the most common cases this would be the
user logged on to the machine.
Two applications that have been successfully tested as vectors for
exploiting this issue are Windows Explorer and Internet Explorer - when
attempting to view network shares containing the '.job' file. File sharing
through MSN Messenger has also been proven to be an effective vector for
attack. In the case of Internet Explorer, this issue could be exploited
simply by viewing a website containing a frame pointing to a network share
containing the '.job' file. Please note that there are many other ways of
exploiting this issue, this is certainly not an exhaustive list.
Fix Information:
Microsoft have provided a fix for this issue which can be downloaded from
the Microsoft Security website at:
<http://www.microsoft.com/technet/security/bulletin/ms04-022.mspx>
http://www.microsoft.com/technet/security/bulletin/ms04-022.mspx
ADDITIONAL INFORMATION
The information has been provided by <mailto:peter@ngssoftware.com> Peter
Winter-Smith.
The original article can be found at:
<http://www.ngssoftware.com/advisories/mstaskjob.txt>
http://www.ngssoftware.com/advisories/mstaskjob.txt
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