Yahoo! Messenger! multiple! vulns!

What do you want to patch today?

There are two new Yahoo Instant Messenger (YIM) vulnerabilities which can potentially compromise a user's machine, Vietnamese researcher Phuong Nguyen has discovered. Yahoo! has been notified and a fixed version is available for download here.

First up, an unchecked buffer which enables any URL beginning with 'ymsgr:' to call ypager.exe, crash it and run malicious code if the messenger is integrated with the browser. All that's needed is 268 bytes to overflow the buffer, and exploit code can be loaded with the user's level of privilege. The 'call', 'sendim', 'getimv', 'chat', 'addview' and 'addfriend' function calls can be exploited, Nguyen says.

Next up a problem with the 'addview' feature which enables the messenger to view Web content on its own. This is vulnerable to freaky URLs and malicious JavaScript and VB script. Yahoo! content can be duplicated and malicious scripts embedded in the HTML to give an attacker numerous means to exploit a target. See Nguyen's original advisory for links to a couple of simple demonstrations (which I've not verified). Yahoo! has removed this particular 'feature' in the fixed version pending further engineering magic to make it safe, Nguyen says. ®

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