Microsoft yesterday issued 10 security updates that patched a record 31 vulnerabilities in Windows, Internet Explorer (IE), Excel, Word, Windows Search and other programs, including 18 bugs marked 'critical'.
Of the 10 bulletins, six patched some part of Windows, while three patched an Office application or component, and one fixed a flaw in IE. Eighteen of the 31 bugs were ranked critical, Microsoft's most serious ranking in its four-step score, while 11 were tagged as 'important', the next-lowest label, and two were judged 'moderate'.
The total bug count was the most patched by Microsoft in a single month since the company began regularly-scheduled updates in 2003. The previous record of 26 vulnerabilities patched occurred in both August 2008 and August 2006.
"This is a very broad bunch," said Wolfgang Kandek, chief technology officer at security company Qualys, "compared to last month, which was really all about PowerPoint. You've got to work everywhere, servers and workstations, and even Macs if you have them. It's not getting any better, the number of vulnerabilities [Microsoft discloses] continues to grow."
Security experts were all over the map when it came to naming which fixes to deploy first.
"IE's, by far, takes the cake," said Andrew Storms, director of security operations at nCircle Network Security. "It's a client-side bug, there are eight CVEs and there's no doubt that it will be exploited."
As Storms said, MS09-019 patches eight separate vulnerabilities in Microsoft's Internet Explorer browser. One of the patches finally plugs the hole that a researcher used in March 2009 to hack IE and walk off with a $5,000 prize at the 'Pwn2Own challenge.
"If you're running IE8 on Windows XP, or are concerned about intranet-based attacks, I would highly recommend putting this update on your high priority 'to do' list," said Terri Forslof, the manager of security response at 3Com's TippingPoint, the Pwn2Own sponsor.
Although users running IE8 on Vista or even Windows 7 are somewhat protected by that operating system from the exploit used to cash in at Pwn2Own, Windows XP users have been at risk for months, Forslof added.
The IE update also caught the eye of Kandek's colleague, Amol Sarwate, the manager of Qualys' vulnerability research lab. "What's interesting is that IE8 only has a single vulnerability," said Sarwate, talking about the Pwn2Own bug. "But IE7 has seven. That's one good reason to go to IE8."
Eric Schultze, chief technical officer at Shavlik Technologies, added two other updates to Storms' IE patch as his fix-first recommendation. "I'd equally patch the IIS, IE and Active Directory vulnerabilities," he said.
The Internet Information Server (IIS) flaw affects some systems that have enabled WebDAV (Web-based Distributed Authoring and Versioning), a set of extensions to HTTP used to share documents over the web. Schultze put the spotlight on MS09-020 because Microsoft had publicly acknowledged the bug last month in a security advisory.
MS09-018 got his attention because Microsoft labelled the Active Directory flaw as critical, and it could be exploited remotely by simply sending a server a malicious data packet. "Someone could use this to take over Active Directory, and if they do, they'd own all [an organization's] passwords," Schultze said.
Three of the security updates, MS09-021, MS09-024 and MS09-027, addressed one or more issues each in Microsoft's popular Office suite.
None of the researchers contacted put the Office patches near the top of their to-do list. Storms explained why: "Office in general is usually not without bulletins," he said. "This month it's Excel, Works Converter and Word. It's going to continue happening," he said, referring to the file format parsing bugs that continue to plague Office. "It's easy to write fuzzers for file format parsing problems, and while Microsoft's fuzzers may be more sophisticated, there are more hackers out there than Microsoft has employees."
Kandek and Sarwate nominated MS09-022, a three-patch update for the Windows print spooler. "It affects all Windows operating systems, anyone can activate this, and most people have remote printing enabled on their PC," said Kandek. "An additional aspect is that this is often out of the control of the IT administrator, since it's easy for users to turn on remote printing."
Microsoft wasn't able to wrap up work on a patch for a known vulnerability in DirectX, specifically in the QuickTime format parser within DirectShow. The no-show was no surprise, since the company had announced it wouldn't issue a fix today in its monthly advance notification last week.
"I'd expect to see that next month, though," said Storms.
The company, however, did release security updates for the Mac editions of PowerPoint; last month, Microsoft took the unusual step of issuing fixes for the Windows versions, but not for the Mac. At the time, it explained the decision as wanting to protect most users immediately rather than wait to protect everyone later. One researcher, however, blasted Microsoft for breaking its own rules for "responsible disclosure".
Other bulletins that Microsoft released today patched problems in Windows Search (MS09-023), Windows' kernel (MS09-025) and Windows' remote procedure call (RPC) function (MS09-026).
"Ten is a large number, but at least two in the past year were larger," said Schultze, talking about the number of security updates released yesterday. And three are on the server side, where a hacker can remotely attack without any user interaction. Those are the ones that are frequently leveraged in worms."
June's updates can be downloaded and installed via the Microsoft Update and Windows Update services, as well as through Windows Server Update Services.