Apple has released a massive security update for Mac OS X along with a new version of its OS, however, according to several reports, installing the patches could render computers unbootable.
The Mac OS X Security Update 2011-006 addresses more than 70 vulnerabilities in core components, as well as third-party products bundled by default with the OS.
Many of the flaws have the highest severity rating assigned to them and can result in arbitrary code execution through a remote attack vector.
Two security issues were patched in the Mac OS X kernel, one in CoreStorage, two in CoreMedia, while others were in CoreProcesses, CoreFoundation, CFNetwork, and even the application firewall.
With this update Apple also played security catch-up with many third-party software packages that provide important functionality, such as Apache HTTPD, BIND, PHP, Tomcat, Mailmain, Python, or libpng.
QuickTime, a central application in Apple's ecosystem, was also updated in this release to address 11 different vulnerabilities. However, some of them only affect OS X Snow Leopard.
Despite the benefits of the security update, users should carefully weigh whether to install it. That's because, according to some reports, the update can result in serious issues.
"Apple OSX Security Update makes macbook kernel panic at boot," warned security researcher Dragos Ruiu Thursday on Twitter. He later confirmed that other users have experienced similar problems, particularly on systems with Lion/Snow dual-boot configurations. "If you have two or more os partition on mbp [MacBook Pro] it breaks," the security expert said.
Meanwhile, Graham Cluley, a senior technology consultant at Mac OS antivirus provider Sophos, reported installation errors for the newly released iOS 5 mobile OS. He couldn't confirm the Mac OS X boot issues, but advised users to postpone updating if they believe they might be affected.
"My advice would be to contact Apple technical support - and see if they have a resolution for the problem. If you suspect you may be impacted by the issue it may be wise to hold off installing the security update until Apple has confirmed if it has fixed it," Cluley said.
Apple's new Mac OS X Lion v10.7.2 contains most of the security patches from Security Update 2011-006, and there are reports that it too is causing issues for adopters. Reports like "After updating to Lion 10.7.2 System now hangs on boot" or "Mac forced me to restart after updating to 10.7.2" started appearing on the Apple support forums.
One user suggests that resetting the PRAM after the update might solve the problem. Apple did not immediately respond to a request for comment.