Microsoft on Thursday chalked in four security updates for next week that would fix vulnerabilities in Windows, SQL Server and Exchange Server.

All four were labeled "important," the company's second-highest ranking, even though one of the Windows updates will quash a bug that attackers could use to execute malicious code remotely. That kind of vulnerability has been regularly rated as "critical" by Microsoft in the past.

As is its practice for pre-patch notifications, Microsoft disclosed few details Thursday of next week's updates other than their severity ranking and the affected software.

"None of these were on my radar," admitted Andrew Storms, director of security operations at nCircle Network Security Inc. "I'm doing quite a bit of head scratching given the variety and interesting details [in the bulletins]."

One of the two Windows bulletins will patch Windows 2000 and Windows XP -- including the recently released XP Service Pack 3 (SP3) -- but not Windows Vista, while the second update slated for the client operating system will patch Vista, including Vista SP1, but not the older OSes.

The Vista bug caught Storms' eye because while Microsoft said it could result in remote code execution -- a description reserved for a serious vulnerability that could let hackers hijack a PC -- the company ranked it as important, not critical.

"I read that kind of bug as 'critical'," said Storms. "Microsoft seems to have stepped it up a notch," he said, noting that it appears the company is taking a harder line in defining "critical" flaws as only those that don't require any user action to be exploited.

Microsoft described both the SQL Server bug and the Exchange vulnerability as elevation of privilege flaws, and will provide patches for the former to Windows Server 2003, Server 2008, Windows 2000 and all still-supported versions of SQL Server, the company said. The Exchange update applies to both Exchange Server 2003 and the newer Exchange Server 2007.

The amount of detail Microsoft tucked into the pre-patch notification for the SQL Server and Exchange Server vulnerabilities puzzled Storms, who pointed out that Microsoft specified that the former's flaw affected both WMSDE, the SQL engine added to Windows clients, and WYukon, the engine within Windows server software. "I don't know whether this is a clue [about the vulnerability] or whether they're just being more promiscuous with information," Storms said.

It doesn't appear the Microsoft will be patching an Internet Explorer vulnerability first reported in 2006, but which returned to the limelight last month when security researcher Aviv Raff claimed that it could be combined with a bug in Apple Inc.'s Safari to pose a danger to users. At the end of May, Microsoft warned users of the blended threat, and recommended that people stop using Safari.

Apple patched Safari for Windows to quash the browser's so-called "carpet bomb" bug two weeks ago.

But Storms thought there was an outside chance that Microsoft would fix IE, even though it didn't explicitly label any of the prospective patches as intended for Internet Explorer. Last year, he said, Microsoft dealt with protocol handler bugs that could be exploited by attacks against IE by fixing Windows, not the browser.

The four security updates will be posted Tuesday, July 8, around 1 p.m. EDT.