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The Macintosh OS X Operating System provides built-in support for both BinHex and MacBinary file types. These file types allow for the efficient transfer of information across networks by allowing information to be compressed by the sender and then decompressed by the recipient. This capability is particularly useful on the Internet, allowing users to download-compressed files.
A vulnerability results because of a flaw in the way Mac OS X and Mac IE 5.1 interoperate when BinHex and MacBinary file types are downloaded. As a result, an application that is downloaded in either of these formats can execute automatically once the download is complete.
A user would first have to choose to download a file and allow the download to fully complete before the application could execute. In addition, users can choose to disable the automatic decoding of both these file types. |
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Credit:
The information has been provided by Microsoft Product Security.
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Vulnerable systems:
* Microsoft Internet Explorer 5.1 for the Macintosh
Mitigating factors:
* The user would have to choose to download the application before any attempt could be made to exploit the vulnerability. It cannot be exploited without user interaction.
* The application would have to successfully download before any attempt could be made to exploit the vulnerability. The user can cancel the download at anytime prior to completion.
* The vulnerability could not be exploited if automatic decoding of BinHex and MacBinary files has been disabled. This is not a default setting however.
Patch availability:
Download locations for this patch
* Microsoft IE 5.1 for Mac OSX:
Users must use the Software Update feature of Mac OS X v10.1 to install the "Internet Explorer 5.1 Security Update."
More information on Software Update is available at: http://www.apple.com/macosx/upgrade/softwareupdates.html.
What's the scope of the vulnerability?
This vulnerability could allow an application to execute unexpectedly. If an attacker enticed the victim to download a malicious program compressed as a BinHex or MacBinary file type, the program could execute after the download completed.
For this attack to succeed, the user would have to initiate the download process. This vulnerability cannot be used to automatically download and execute malicious code on the users system.
What causes the vulnerability?
The vulnerability results because an issue with how IE and the Mac OS interoperate when handling downloaded MacBinary and BinHex files.
What are BinHex and MacBinary files?
BinHex is a utility that encodes Macintosh files so that they can travel well on networks. BinHex encodes a file from its 8-bit binary or bit-stream representation into a 7-bit ASCII set of text characters. The recipient decodes it at the other end.
MacBinary is a format for binary transfer of Macintosh documents over a telecommunication link. It is intended for use between Macintoshes and in uploading Macintosh documents to remote systems.
How could an attacker exploit this vulnerability?
An attacker would need to host an executable file on a web site, packaged as either a BinHex or MacBinary file, and then entice another user to visit the site and initiate a download. Once the download was complete, the executable file would automatically execute.
What does the patch do?
This patch updates Internet Explorer 5.1 to version 5.1.3 (build 3905) and prevents the Mac OS from automatically launching MacBinary and BinHex files.
Where can I download the patch or how do I update my OS?
Users must use the Software Update feature of Mac OS X v10.1 to install the "Internet Explorer 5.1 Security Update."
More information on Software Update is available at: http://www.apple.com/macosx/upgrade/softwareupdates.html.
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