Karthik Raman, a researcher with McAfee, first reported in a Tuesday blog entry that Chinese researchers were claiming to have found a zero-day bug in Yahoo Messenger. On Wednesday, Raman's fellow McAfee researcher Wei Wang noted in a blog entry that they have been able to reproduce the vulnerability on Messenger V220.127.116.113.
"It seems like a classic heap overflow, which can be triggered when the victim accepts a Webcam invite," wrote Wang.
The bug, according to McAfee, may enable user-assisted remote-code execution attacks. Raman had noted that they have not seen any exploit code for this flaw published yet.
McAfee said it has contacted Yahoo's security team and notified it of the problem.
"Since learning of this issue, we have been actively working towards a resolution and expect to have a fix shortly," said a Yahoo spokesman in an e-mail to InformationWeek. "Yahoo takes security seriously and consistently employs measures to help protect our users."
Wang also reported that this vulnerability is different from one that was patched in June. Researchers at eEye Digital Security had reported that there actually were multiple flaws in version 8 of Yahoo's instant messaging client software. Those flaws could enable a remote hacker to take control of a user's system.
A Yahoo spokeswoman had explained that the June issue was a buffer-overflow flaw in an ActiveX control. This control is part of the code for Webcam image upload and viewing.
McAfee's researchers offered up a few recommendations to deal with this latest bug:
- Users should not accept Webcam invites from untrusted sources until a patch for this vulnerability is released and installed; and
- Block outgoing traffic on TCP port 5100 until Yahoo can patch the flaw .