Critical Internet Explorer patch 'does not work'

A fix to a serious bug in Microsoft's browser is still not working properly after a re-release, according to the firm that discovered the flaw

A patch released by Microsoft to fix a critical security vulnerability in Internet Explorer does not work, according to security experts.

The "object type" vulnerability was discovered by eEye Digital Security around four months ago. A patch was released on 20 August -- and then re-released on 28 August, because under some circumstances it caused problems for some non-default operating system installations -- and looks due for yet another re-release because it simply doesn't fix the vulnerability it is supposed to, eEye said.

The vulnerability can be exploited by crafting a malicious HTML file that, when viewed by an Internet Explorer browser, extracts and executes malicious code.

Speaking to ZDNet Australia by phone from the US, Marc Maiffret, eEye's chief hacking officer, said the vulnerability is particularly critical because it doesn't take a lot of effort to take advantage of. "It's pretty serious just because it's so easy to exploit... it doesn't require someone to know how to write buffer overflow exploits or anything like that."

Maiffret says Microsoft should have done a better job to begin with. "How do you take four months to fix something this simple and then not fix it correctly?" he asked. "It seems like they are taking security seriously... [but] at the same time I don't think they're really investing."

The lack of suitably skilled security engineers within the company is one reason Maiffret says this incident -- described by the researcher who discovered the flaw in the patch as a "pathetic oversight" -- has occurred. "A lot of it comes from having the right people in-house," Maiffret said. "They have some very smart guys in there, but they definitely don't have enough."

The problem with the security fix was first made public by malware.com and Maiffret sincerely doubts that Microsoft were informed prior to the disclosure. "They discovered it and they're getting the information out there... I'm not sure if they gave Microsoft the information, which is usually the best way," he said.

Prior to the release of the patch, Maiffret's team looked over the patch and didn't see any problems, but he says it was a quick "once over" -- not a detailed audit. "[Our] researchers were just helping out, it's not like MS were paying us for this," he said. Microsoft use external security code auditors, which in this case were not doing enough, Maiffret says.

Concerned users can disable active scripting on their browsers to mitigate the vulnerability until Microsoft makes a patch available.