Microsoft Internet Explorer allows arbitrary local file reading via "showHelp()" function

Overview

A vulnerability in Microsoft Internet Explorer (IE) allows remote attackers to read arbitrary files on a vulnerable system.

Description

A vulnerability in the showHelp Method contained within IE may allow a remote attacker to read arbitrary files. For further details, please see the following documents:

* [Sandblad #11: showHelp("file:") disables security in IE](<http://online.securityfocus.com/archive/1/310684>)
* [Microsoft Security Bulletin MS03-004](<http://www.microsoft.com/technet/treeview/?url=/technet/security/bulletin/ms03-004.asp>)

Although a patch is available, it is important to note that it disables the showHelp method, but does not “fix” it. In order to restore the functionality showHelp provides, you must install the latest version of HTML Help. Additionally, the latest version of HTML Help contains some limitations. Quoting from Microsoft Security Bulletin MS03-004:

* _Only supported protocols can be used with showHelp to open a web page or help (chm) file._
* _The shortcut function supported by HTML Help will be disabled when the help file is opened with showHelp This change will not affect the shortcut function if the user opens the same CHM file manually by double-clicking on it, or by invoking an application on the local system that uses the HTMLHELP( ) API._

Microsoft recommends using <http://windowsupdate.microsoft.com/&gt; to obtain the latest version of HTML Help.

Impact

A remote attacker may be able to read arbitrary files on a vulnerable system, which may allow them to gain access to sensitive information such as user credentials. In the worst case, a remote attacker may be able to execute programs with certain parameters leading to a total system compromise if IE is running as administrator.

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Solution

Apply a patch. More information about patches can be found in MS03-004.

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Vendor Information

400577

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Microsoft Corporation __ Affected

Updated: February 06, 2003

Status

Affected

Vendor Statement

See <http://www.microsoft.com/technet/treeview/?url=/technet/security/bulletin/ms03-004.asp&gt;.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%23400577 Feedback>).

CVSS Metrics

Group	Score	Vector
Base
Temporal
Environmental

References

• <http://www.microsoft.com/technet/security/bulletin/ms03-004.asp&gt;
• <http://www.microsoft.com/security/security_bulletins/ms03-004.asp&gt;
• <http://online.securityfocus.com/archive/1/310684&gt;
• <http://windowsupdate.microsoft.com>

Acknowledgements

This vulnerability was discovered by Andreas Sandblad. The CERT/CC thanks Andreas for helping us to understand this vulnerability.

This document was written by Ian A Finlay.

Other Information

CVE IDs:	CVE-2003-1328
Severity Metric:	28.69 Date Public: