[NT] Unchecked Buffer in mstask.dll
From: SecuriTeam (support_at_securiteam.com)
To: firstname.lastname@example.org Date: 18 Jul 2004 16:20:13 +0200
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Unchecked Buffer in mstask.dll
When thinking about buffer overflow vulnerabilities, a file can sometimes
be as harmful as a packet. Even though past security issues have taught us
that it is unwise to use an unvalidated text string containing a file name
or directory, that is what happened here.
By creating a .job file with a large "to be executed" field the stack can
be overwritten allowing for remote command execution, when the file is
parsed by mstask.dll.
* Microsoft Windows 2000 Service Pack 4
* Microsoft Windows XP, Microsoft Windows XP Service Pack 1
It appears that both explorer.exe and iexplore.exe will parse a .job file
when showing folder listings. Upon the parsing of the .job file, the large
"to be executed" field is passed to wcscpy without doing any bounds
Using explorer the viewing of a folder containing the .job is enough to
cause the buffer overflow to occur. The file can be hosted locally or on a
remote network share. A remote attack would require the end user to visit
the folder/share containing the exploit file.
Using Internet Explorer the viewing of a folder containing the .job file
through the use of an [iframe] object will cause the buffer overflow to
Viewing an HTML email that is based around the [iframe] attack avenue,
will also cause the buffer overflow. This will occur without any user
intervention if the preview pane is enabled, or with user intervention by
viewing the email.
It is possible that there are other avenues of attack to exploit this
Remote exploitation through Internet Explorer can be obtained through the
use of an iframe object pointing at an anonymous share.
Automatic exploitation of browser based bugs, does not rely on an attacker
sending a link, requiring the target user to click on it. Links,
references and other objects can easily be opened through script code. And
Brett was told that this can also be achieved without script code.
- Install the vendor supplied patch:
The information has been provided by
<mailto:email@example.com> Brett Moore.
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