Microsoft has patched five vulnerabilities in Windows and Office, including a bug hackers have been exploiting for almost a month.
As expected, today's patch schedule was short: just four security updates that included fixes for five separate flaws. Of the four updates, three were rated "critical", the highest threat ranking in Microsoft's four-step scoring system. All five of the specific vulnerabilities patched today were also rated critical.
Two of the bulletins affected Windows, while the remaining pair impacted Office. Four of the five vulnerabilities in the bulletin quartet were pegged by Microsoft with an exploitability index score of '1', meaning that the company expects attacks to materialise in the next 30 days.
The most prominent of the pair was MS10-042, the update that addressed the vulnerability in Windows XP's Help and Support Center, a feature that lets users access and download Microsoft help files from the Web and can be used by support technicians to launch remote support tools on a local PC.
In early June, Tavis Ormandy, a security engineer who works for Google published attack code for the bug - which also affected Windows Server 2003 - and immediately unleashed a heated debate. While some security researchers criticised Ormandy for taking the bug public, others rose to his defence, blasting both Microsoft and the press for linking Ormandy to his employer.
Ormandy disclosed the vulnerability five days after reporting it to Microsoft after he said the company wouldn't commit to a patching deadline. Microsoft has disputed that, claiming that it only told Ormandy it would need the rest of the week to decide.
Users and IT administrators should apply the MS10-042 patch as soon as possible, agreed several researchers. "This is actively being exploited to target XP desktop systems," said Jason Miller, the data and security team manager for Shavlik Technologies. Miller also noted that Windows XP remains the most-popular version of Windows on both consumer and business PCs, a fact that Microsoft itself stressed yesterday when a company executive said that XP was on 74% of all corporate machines.
"I'm impressed that Microsoft was able to do a turnaround on this as quickly as they did," said Miller. "Some bugs linger for months out there."
Microsoft was first told of the Help and Support Center flaw on June 5, and confirmed that by June 15, attacks were exploiting the bug.
The other Windows update, MS10-043, patches a single bug in the 64-bit version of Windows 7 and Windows Server 2008 R2. Microsoft confirmed the vulnerability in May with a security advisory, noting then that the flaw was in Windows' Canonical Display Driver, which blends the operating system's primary graphics interface, dubbed Graphics Device Interface (GDI), and DirectX to compose the desktop.
At the time, Microsoft told users to disable the Aero interface, which is the default on all but the least-expensive editions of Windows 7. Aero is an optional install on Windows Server 2008 R2.
According to Oliver Lavery, the director of security and research and development for nCircle, the Windows 7 vulnerability was due to a programming error on Microsoft's part when it ported the relevant code from the 32-bit version of Windows to the 64-bit version of Windows 7.
The other pair of updates fixed flaws in Access, the database included with some versions of Office, and Outlook, Microsoft's business e-mail client.
Of the two, the most interesting to Richie Lai, director of vulnerability research at Qualys. was MS10-045. "The vulnerability undermines the security model of Outlook, because attackers can make any file type look like any other file type," Lai said. "That's scary, because it makes all attachments dangerous to open, not just those file types people are cautious about."
Hackers could disguise attack code as, say, a .txt, .pdf or .jpg file type, Lai continued, to more easily dupe users into opening and launching the malware. "Those kinds of files most people will click on without thinking twice," said Lai. "And it bypasses all the prompting that normally displays," he added, referring to the warnings that Outlook normally shows when potentially-dangerous file types are clicked.
Others, including Miller from Shavlik and nCircle's Lavery, echoed Lai's take on the Outlook bug. "This one is interesting because it bypasses the security warnings," said Lavery. "Attackers would have to host their malicious code on their own server, so this isn't a direct attack, but it's certainly a flaw in [Outlook's] warning mechanism."
According to Microsoft, all currently-supported versions of Outlook, with the exception of Outlook 2010, contain the vulnerability and must be patched.
The fourth update, MS10-044, addressed two bugs - one rated critical the other ranked "important," the next threat step down - in ActiveX controls used by Access.
"It's a bit shocking, really," said nCircle's Lavery. "ActiveX is practically a dead technology, but people are still finding vulnerabilities in it. I've been doing this for 10 years, and even now, Microsoft hasn't managed to kill off all the bugs. It's just silly."
Because Microsoft now ships alternating large and small batches of fixes, with the larger updates landing in even-numbered months, researchers expect that the patch count will be considerably larger next month. Microsoft will deliver its next slate of fixes August 10.
This month's security update can be downloaded and installed via the Microsoft Update and Windows Update services, as well as through Windows Server Update Services.