Microsoft is rushing out a fix for a Windows Web Server flaw that is starting to be exploited by online attackers.
The patch fixes a bug in the Windows ASP.net technology used in Microsoft's servers. Microsoft says it's seen "limited" exploitation of the flaw in online attacks, but the problem is serious enough that the company has decided to rush out a fix ahead of its next regular patch update, scheduled for October 12.
ASP.net is used to build web applications, and the bug gives attackers a way to gain access to protected files or read encrypted data sent by an ASP.net application server. Earlier this month, researchers demonstrated how the attack could be used to steal encrypted session cookies or possibly even user names and passwords from websites.
Microsoft occasionally does this type of out-of-band update when it spots a serious security problem, but this release is different. For the first time, Microsoft will initially release the patch only at the Microsoft Download Center - typically used by users at large organisations who want to test the patches before manually installing them companywide.
"This enables us to get the update out as quickly as possible, allowing administrators with enterprise installations, or end users who want to install this security update manually, the ability to test and update their systems immediately," Microsoft said in a blog.
"We strongly encourage these customers to visit the Download Center, download the update, test it in their environment and deploy it as soon as possible."
For most consumers, who rely on automatic updates, the patch is still a few days away. Consumers aren't vulnerable to the bug, however, unless they happen to be running a web server on their computer.
Microsoft will release the update in the Download Center this week. The company didn't give a date for the broader, automatic update.
"This is the first time we've released [an] update this way, but due to the nature of the active attacks and the severity of the potential loss of data, we are releasing the security update to the Microsoft Download Center first so customers (specifically large enterprises, hosting providers, and ISVs) can begin updating their systems," Microsoft said. "Within a few days we will distribute the update through the rest of our standard distribution channels."