MS IE patch misses the mark

Partial fix leaves 12 outstanding bugs

Microsoft's latest cumulative patch for Internet Explorer fails to tackle at least one of the problems it is meant to fix, and leaves a dozen reported security bugs unpatched.

That's according to postings by Danish security researcher Thor Larholm and GreyMagic Software to security mailing list BugTraq, which point to a number of shortcomings with the patch.

In its advisory, Microsoft refers to the most serious of the six bugs as a "cross-site scripting vulnerability in a Local HTML Resource".

But security watchers say the problem is worse and involves the bypass of dialogArguments security restrictions (which is supposed to prevent objects being passed to a dialog).

Attackers could by using this flaw elevate privileges; hijack MSN Messenger; run script in the My Computer zone; and perform arbitrary command execution.

Microsoft has only patched a symptom to the problem and not its root cause, argues GreyMagic Software, while Larholm takes issue with Microsoft arguments that the bug could not be automatically exploited. In so far that Microsoft has alleviated the problem it has only done so with IE6 - IE5.01 and IE5.5 are still vulnerable, he argues.

In support of these arguments, GreyMagic Software refers users to some harmless examples of exploitation, of the vulnerability and Larholm's original advisory.

Microsoft's partial patch leaves users largely vulnerable to malicious exploits along similar lines, but thankfully simply disabling scripting provides an effective workaround to the problem.

More problems with partial patch

Larholm criticises other aspects of the cumulative patch on much the same grounds, and concludes that many security problems with the browser remain outstanding.

"Yesterday I hosted a list of 14 publicly known unpatched vulnerabilities, today I host a list of 12 such," he concludes. ®

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