Software Engineering Institute

Safari

Apple Safari is a web browser that comes with the Mac OS X operating system.

Explicit binding

Mac OS X supports a feature called explicit binding, which LaunchServices examines to determine which application is used to open a file. If explicit binding is specified for a file, this setting will override the application association for the file type. Explicit binding information is stored in the resource fork for a file.

"Safe" files

By default, Safari will automatically open "safe" file types, such as pictures, movies, and archive files, including ZIP files. If the contents of an archive file are also considered safe, then Safari will automatically open the contents after the archive is extracted.

The problem

A data file with explicit binding can allow an attacker to execute arbitrary commands or code on systems running Safari. Limited testing shows that Safari apparently fails to check for the presence of explicit binding data when determining if a file is "safe" or not.

By convincing a user to view a specially crafted HTML document (for example, a web page), an attacker may be able to execute arbitrary commands or code with the privileges of the user.
Proof of concept code is publicly available.

Install an update
Install Apple Security Update 2006-001 and Apple Security Update 2006-002, which provide updates to Safari, LaunchServices, and CoreTypes. These updates improve the method that Safari uses to determine if a file is safe.

Disable "Open 'safe' files after downloading"

Disable the option "Open 'safe' files after downloading," as specified in the Securing Your Web Browser document. This will help prevent automatic exploitation of this and other vulnerabilities.