Credit: John David Bigl III
UPDATED 12 pm Aug. 28, 2014, with Microsoft reissuing the patch without bugs.
One of Microsoft's recent security patches has created an even worse bug than it patched: Under certain circumstances, the faulty patch causes Windows computers to crash, reboot and then get stuck in an infinite rebooting loop.
Microsoft has since recalled the patch. For people already caught in the perpetual "blue screen of death" (as Windows crash screens are often called) the company has issued a workaround that people can use to get their computers up and running again.
The faulty patch, officially documented as MS14-045, was intended to address some issues in the Windows kernel, affecting all supported versions of the Windows operating system (Vista; Windows 7; Server 2003, 2008, 2008 R2, 2012, 2012 R2; Windows 8 and 8.1; Windows RT and RT 8.1 and Server Core installations).
MS14-045 was released last Tuesday (Aug. 12) as part of Microsoft's monthly "Patch Tuesday" security updates. Some users quickly found that the patch was itself a bug, but only for computers that had an OpenType Font (OTF) file installed and saved in a location other than the default font directory.
Those circumstances are so specific that Microsoft's pre-release patch testing didn't catch the flaw.
Microsoft has released instructions for how to break the reboot loop on its support page. Essentially, the instructions boil down to restarting a computer in Safe Mode, booting from an installation CD or USB or putting the computer in the Windows Recovery Environment, then finding and deleting a file named fntcache.dat.
UPDATE: Microsoft reissued the patch Aug. 27 without the faulty components.
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Jill Scharr is a staff writer for Tom's Guide, where she regularly covers security, 3D printing and video games. You can follow Jill on Twitter @JillScharr and on Google+. Follow us @tomsguide, on Facebook and on Google+.