Microsoft Rushes Out Fix for Major Hole Caused by Previous Meltdown Patch

Microsoft has rushed out an out-of-cycle security patch to address problems created by what were supposed to be fixes for the Meltdown vulnerability that it had previously issued for 64-bit Windows 7 and Windows Server 2008 systems.

In an advisory Thursday, the company urged anyone running Windows 7 for x64 systems or Windows Server 2008 R2 for x64-based systems to immediately install the new update. The advice applies to all organizations and users that have installed any of Microsoft's security updates during or after January 2018.

The update for CVE-2018-1038 stems from a warning by Swedish penetration tester Ulf Frisk that Microsoft's Meltdown patch for Windows 7 and Windows Server 2008 created a bigger hole than the one the patch was designed to fix.

The patch basically allowed any running process on these systems to read the complete contents in memory and to write to it as well. "Exploitation was just a matter of read and write to already mapped in-process virtual memory," Frisk said. "No fancy APIs or syscalls required — just standard read and write." The problem stemmed from a permission bit in a key memory table being set in "user" mode rather than "supervisor" mode.

"This made the page tables available to user-mode code in every process," rather than only by the kernel itself, Frisk said.

Chris Goetti, director of product management at Ivanti, says the vulnerability created by the Microsoft patch is pretty significant and something that needs to be addressed with haste, if possible.

"When Microsoft issued a fix for Windows 7 and Windows Server 2008, they made a mistake and ended up opening up read and write access in RAM so anybody could access anything in memory and write to it," he says. "It is a significant vulnerability and leaves those systems pretty much exposed" without the update.

At this point, those with affected systems should test the new patch quickly and roll it out. Another option for those that don't have the time to test the new patch will be to roll back the March update and wait for Microsoft's April update, which is due April 11.

"We are close to the April update," Goetti says. "Our guidance is to either apply the new update or roll back the March update," for Windows 7 x64-bit systems and Windows Server 2008 x64-bit systems, he says.

Organizations should not make the mistake of assuming the issue is related to Meltdown/Spectre and wait for things to settle down, cautions Jack Danahy, CTO and co-founder of Barkly. "This is an easy-to-exploit zero-day vulnerability and a much more probable attack vector that the original problem that Microsoft was trying to correct."

Unlike problems created by Spectre and Meltdown, "this isn't just a cleanup exercise. Microsoft accidentally distributed a new zero-day vulnerability of their own design."

The error is an example of the kind of issues that can crop up when things are rushed, he says. Fixing bugs is akin to serious software development, and it creates the same opportunities for mistakes, Danahy notes.

"I think that this will only serve to further deteriorate organizational willingness to apply patches automatically and without their own testing," he says. "I'm personally hoping that everyone deploys this patch to CVE-2018-1038, because this vulnerability is so easy to exploit that there are already exploit toolkits integrating it."

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