[ GFISEC04102001 ] Internet Explorer and Access allow macros to be executed automatically

["Sandro Gauci" <sandro () gfi com>]

GFI Security Labs Advisory
http://www.gfi.com/



----[Title: 

[ GFISEC04102001 ]   Internet Explorer and Access allow macros to be 
                     executed automatically



----[Published: 

12.FEB.2002


----[Vendor Status:

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



----[Systems Affected: 


Windows machines with :

   * Microsoft Access

     and

   * Internet Explorer version 5 till version 6. Older versions may be 
     vulnerable as well.

   * Outlook Express 2000,

   * Outlook Express 98,

   * Outlook 2000,

   * Outlook 98

   * possibly other HTML and/or 
     Javascript enabled email clients.



----[The problem:


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

The problem is exploited by embedding a VBA code within a
Access database file (.mdb) within an Outlook Express email 
file or Multipart HTML (mht) file. 

If the email file is accessed using Internet Explorer, the 
attachment may be automatically executed without triggering 
any security alerts. The exploit will work regardless of 
the security level (in our labs, we also tested it with High 
Security and Restricted Zone).

This may be exploited through email by using an iframe 
tag or using Active Scripting to call the malicious file 
through an HTML email, allowing Internet Explorer to 
automatically access the exploit EML file.



----[Proof of concept Exploit:

A live example of the named exploit is available on:

http://www.gfi.com/emailsecuritytest


----[Solution:

Filtering HTML email for JavaScript and similarly scripting 
capabilities as well as checking for IFRAME will prevent the 
exploit to be run through email. This can be easily done 
using GFI's Mail essentials & Mail Security for Exchange 2000.

GFI Security Labs also recommends filtering out mdb files.

You might also want to consider blocking access to EML, 
MHTML and MHT files through HTTP and SMTP. It is also 
important to apply the patch distributed by Microsoft.



----[Reference:

http://www.gfi.com/emailsecuritytest


----[Contact Information:

Sandro Gauci
GFI Security Labs
sandro () gfi com
http://www.gfi.com


GFI - Security & communications products for Windows NT/2000
http://www.gfi.com

**********************************************************
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your email users. Spam, viruses, dangerous attachments & offensive
content can be removed before they reach your mail server.
In addition it has server-based email encryption, disclaimers
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