Microsoft has patched 15 vulnerabilities in its operating system, browser, and other software in its June update, known as Patch Tuesday. However, security experts cannot agree on which problems should be fixed first.
The month's six updates fixed multiple bugs in all currently-supported versions of Windows; in Internet Explorer (IE), both IE 6 and IE 7; in yet another member of the Office family; and in the entry-level email clients Outlook Express and Windows Mail. Of the 15 flaws, nine were labelled critical, Microsoft's most serious threat ranking, while two were pegged as important and two judged moderate.
Unlike in other months, however, when researchers have usually reached a consensus on which patches should be deployed first, users received mixed messages.
"We think MS07-031 and MS07-035 should be patched first," said Amol Sarwate, the manager of Qualys' vulnerability research lab. "They both affect the core of the Windows operating system, and require no additional software to exploit."
MS07-031 should be tops because it may let attackers, phishers particularly, not only fake out users but feed them malware, he said. A bug in Windows 2000, XP and Server 2003's handling of Secure Socket Layer (SSL) could "give users a false sense of security when they connect to a secure site," said Sarwate.
"The server gives the appearance of a secure site, but instead can send remote code," Sarwate said. Because the bug is in Windows, the vulnerability is browser independent, added Jonathan Bitle, Qualys' manager of technical account management.
But David Dewey, research manager at IBM's Internet Security Systems X-Force team, dismissed MS07-031. "It looks bad and at first glance it's the one for this month, but it's not exploitable," said Dewey. X-Force's research, he said, showed that the bug couldn't be exploited with any known attack technique. "No one will exploit this in the near term," he said. "A working exploit would take a new discovery in how exploits are made."
Instead, Dewey recommended that users patch MS07-033, a six-bug update to IE6 and IE7, and MS07-030, which patches a pair of problems in Microsoft Visio, the business and technical drawing application that's part of the Office line-up. Dewey stuck to his guns, even when reminded that the Visio fixes were only ranked moderate.
"Both are very similar to other vulnerabilities that attackers have leveraged," he explained. The Visio vulnerabilities can be exploited, he added, using malicious documents - a trend hackers have widely used since the beginning of 2006 in targeted attacks against selected individuals.
Symantec's researchers also urged users to plug the holes in IE quickly. "[We] rate the vulnerabilities in Internet Explorer as the most critical since two affect Internet Explorer 7 on Windows Vista," the company's response team said in an emailed alert. As with many of the bugs Microsoft patched Tuesday, the half-dozen in IE require some kind of user interaction to be successfully exploited; the most likely route to attack would be spammed email that links to a malicious website.
Vista, Microsoft's newest operating system, was also affected by MS07-034, a four-bug update to Outlook Express on Windows XP and Windows Server 2003, and its replacement on Vista, Windows Mail. But while the Outlook Express bugs rated low, moderate or important threat warnings, Microsoft pinned a critical label on the Windows Mail flaw.
The third Vista-related update, MS07-032, caught Sarwate's eye for a different reason. "This is the first bulletin that affects only Vista, and should be noted because of that," he said. "In the past, vulnerabilities in Vista were also found in reused code" drawn from earlier editions of Windows. "This vulnerability is in the brand new code written specifically for Vista."
In the past, Sarwate has criticised Microsoft for reusing older, buggy code in Vista, and has questioned whether the developer's Security Development Lifecycle had been effective.
Updates are available from the Microsoft Update and Windows Update services, and through Windows Server Update Services (WSUS).