A bug in Yahoo Messenger that first surfaced on a Chinese security forum can be used to hack a Windows PC, McAfee researchers confirmed yesterday.
The vulnerability, apparently a heap overflow bug, can be exploited by duping a user into accepting a malicious webcam invitation, said Wei Wang, a Beijing-based researcher with McAfee's Avert Labs.
"We got a chance to dig a bit deeper into this and were able to reproduce the vulnerability on Yahoo Messenger version 220.127.116.113 based on the information provided in the forum," Wei said on the Labs blog.
Yahoo's security team has been told of the bug and its exploit, Wei added.
Wednesday's zero-day vulnerability is Messenger's second in the past 30 days, and its third since early June. Last month, a researcher posted news of a buffer overflow in the instant messaging client triggered by a malformed address book entry. The bug has not been patched, even though a Yahoo spokeswoman said July 17 that one would be issued "shortly."
In June, eEye Digital Security fingered Messenger for a critical ActiveX vulnerability in the software's webcam feature; Yahoo patched that bug June 7.
"[Today's] vulnerability is different from the recently patched one in June," Wei said. Until the IM client is patched, McAfee recommended users ignore unexpected webcam invites and block outbound traffic on TCP port 5100.
As in July, a Yahoo spokeswoman said the company was "working toward a resolution and expect[s] to have a fix shortly."