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[ GFISEC04102001 ] Internet Explorer and Access allow macros to be executed automatically
From: "Sandro Gauci" <sandro () gfi com>
Date: Tue, 12 Feb 2002 12:24:00 +0100

GFI Security Labs Advisory


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



----[Vendor Status:

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

----[Systems Affected: 

Windows machines with :

   * Microsoft Access


   * 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:



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.



----[Contact Information:

Sandro Gauci
GFI Security Labs
sandro () gfi com

GFI - Security & communications products for Windows NT/2000

This mail was content checked for malicious code or viruses
by Mail essentials. Mail essentials for Exchange/SMTP is an
email security, content checking & anti-virus gateway that
removes all types of email-borne threats before they can affect
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
and other email features.

In addition to Mail essentials, GFI also produces the FAXmaker
fax server product range & LANguard internet access control &
intrusion detection. For more information on our products please
visit http://www.gfi.com

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  • [ GFISEC04102001 ] Internet Explorer and Access allow macros to be executed automatically Sandro Gauci (Feb 12)
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