Two 'extremely critical' vulnerabilities have been exposed in Yahoo Messenger that could be exploited by malicious hackers to take over a system. The boundary errors have been confirmed in version 8.1.0.249 of the instant messaging software, but other versions may also be affected.
Both software bugs occur within the Yahoo Webcam functionalities of the IM application. The problems occur in the 'ywcupl.dll' file that handles the Webcam Upload, and the 'ywcvwr.dll' file which handles the Webcam Viewer.
Both ActiveX controls can be exploited to cause a stack-based buffer overflow by assigning an overly long string to the Server property and then using the 'Send()' or 'Receive()' actions.
A successful execution of the exploits could allow arbitrary code to be run on the affected machine.
Security firm Secunia rated the flaws at its highest 'extremely critical' level, and said that the problems can be blocked by changing the kill-bit settings for the affected ActiveX controls.
