Microsoft has pulled an ‘important' Windows kernel security fix, less than a week after releasing it, following reports that it was crashing computers.
Microsoft explained in its Patch Tuesday advisory: "[The patch fixes] three privately reported vulnerabilities in Microsoft Windows. The most severe of these vulnerabilities could allow elevation of privilege if an attacker logs on to the system and runs a specially crafted application. An attacker must have valid logon credentials and be able to log on locally to exploit these vulnerabilities."
However, following its release the update reportedly caused a blue screen of death (BSoD) on a number of computers and forced many businesses to reboot their systems.
Microsoft claims the BSoD is caused by a mishandling of a Windows font cache file in certain customers systems and only occurs in very specific circumstances.
Sophos head of technology Paul Ducklin backed Microsoft's claim, saying the firms' tests showed, "you need to have one or more OpenType Font (OTF) files, installed in non-standard font directories, that are recorded in the registry with fully qualified filenames," for the update to cause a crash.
Microsoft has published a workaround fix while it develops a new patch, however Ducklin warned that "it involves a fair amount of fiddling".
Trend Micro security advisor James Walker told V3 that, despite its complexity, the patch pull could spell trouble for many businesses. "Since the vulnerability has been announced and the patch then pulled, there is of course a window of opportunity for cyber criminals to exploit the vulnerability until the patch is supplied," he said.
Microsoft has had to pull several other patches following BSoD reports in the past. The firm was last year forced to pull a separate security update for all versions of its Windows operating system, following reports the patch was breaking user's machines in April 2013.
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