MSHTML Vulnerability in Internet Explorer

Three vulnerabilities exist in the HTML parsing engine for Internet Explorer.

Issue

MSHTML.DLL is the parsing engine for HTML in Internet Explorer. These vulnerabilities are not related to each other except for the fact that all reside within the parsing engine.

1. The first vulnerability is a new variant of a previously-identified cross-frame security vulnerability. A particular malformed URL could be used to execute scripts in the security context of a different domain. This could allow a malicious web site operator to execute a script on the web site, and gain privileges on visiting users' machines that are normally granted only to their trusted sites.
2. The second vulnerability affects only Internet Explorer 5.0, and is a new variant of a previously-identified untrusted scripted paste vulnerability. The vulnerability would allow a script to paste a filename into the file upload intrinsic control. This should only be possible by explicit user action. Once the filename has been pasted into the control, a subsequent form submission could send the file to a remote web site. If the user has disabled the default warning that is displayed when submitting unencrypted forms, the file would be sent without any warning to the user.
3. The third vulnerability is a privacy issue involving the processing of the "IMG SRC" tag in HTML files. This tag identifies and loads image sources - image files that are to be displayed as part of a web page. The vulnerability results because the tag can be used to point to files of any type, rather than only image files, after which point the document object model methods can be used to determine information about them. A malicious web site operator could use this vulnerability to determine the size and MIME type of files on the computer of a visiting user. It would not allow files to be read or changed, and the malicious web site operator would need to know the name of each file.

Affected Products

• Internet Explorer 4.0 and 5 on Windows 95, Windows 98 and Windows NT 4.0

Download

Patch: http://www.microsoft.com/windows/ie/security/mshtml.asp

Further Details

Source: Microsoft Corporation

Reference: Microsoft Corporation

Updated: April 21, 1999

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