Yahoo offered fixes for two security holes in its Yahoo Messenger (YM) application late last week, holes that could have allowed an attacker to run code of their choice or modify content within YM on a vulnerable PC.
A new version of YM which closes the hole was released on May 24 and is available at http://download.yahoo.com/dl/installs/ymsgr/ymsgr_1065.exe.
The vulnerabilities affect Yahoo Instant Messenger version 5, 0, 0, 1061 running on Windows 98, 2000 and XP Pro, according to security researcher Phuong Nguyen, who discovered the flaws in early May. The first vulnerability stems from a buffer overflow in the application that could allow a specially-formatted URL (Uniform Resource Locator) to overrun the memory allocated to a number of YM functions, Nguyen wrote in his alert. Depending on the length of the URL, YM can be crashed or can be made to run code on the target PC, he wrote.
The second flaw concerns the use of information tabs within YM that give users one-click access to customized information from within Messenger. A vulnerable version of YM, used in conjunction with Microsoft Corp.'s Internet Explorer 5.0 or later, can be forced by an attacker using Visual Basic scripts or Java to create new tabs or to alter the content of existing tabs. An attacker could even steal the username and password of the account being used, Nguyen wrote. The patched version of YM which closes this hole does so by removing the tab-adding feature entirely, he added.
Security vulnerabilities in instant messaging clients are becoming more prevalent, as a handful of holes in Yahoo rival America Online Inc.'s Instant Messenger (AIM) application have been found in 2002. Most recently, AOL closed a hole that could have allowed an attacker to run the code of their choice on an affected PC. [See "AOL Instant Messenger hole could run code," May 6.]Instant messaging programs from a wide range of companies are used by millions of users worldwide.