The serious zero-day flaw affecting Adobe Reader and Acrobat now being exploited in online attacks can be defended against in up-to-date versions of the program by enabling 'protected view', Adobe has said.
Windows users of Reader XI 11.0.1 and Acrobat XI could neutralise the flaw (CVE-2013-0640 and CVE-2013-0641) by changing the default security settings in Edit > Preference > Security (enhanced) and then ticking the box that enables Protected View for 'files from potentially unsafe locations', the company revealed in its online advisory.
Windows admins could do the same. "Enterprise administrators can protect Windows users across their organization by enabling Protected View in the registry and propagating that setting via GPO [Group Policy Object] or any other method."
Adobe hasn't revealed what if any effects might occur in enabling this mode beyond being unable to open all received PDFs, but it leaves users of older versions that lack this feature, Reader 9.5.3 through 10.1.5, undefended.
Two days ago, security firm FireEye announced that it had discovered the zero-day flaw, a warning that came in the same week Adobe had released patches for 19 vulnerabilities in Flash/Shockwave Player, almost all rated critical.
More seriously, the new Reader flaw is believed to be the first confirmed as being able to find a way to beat XI's security sandbox.
"We can confirm the existence of a malicious PDF in the wild that's successfully able to break out of Adobe Reader's sandbox," said Kaspersky Lab's senior researcher, Roel Schouwenberg. "We've seen successful exploitation on a machine running Windows 7x64 and Adobe Reader 11.0.1."
An update from FireEye details how the exploits for CVE-2013-0640 and CVE-2013-0641 use a variety of techniques to defeat the sandboxing.
Meantime, with even Reader XI vulnerable, the best users can do is await the fix from Adobe that has been promised.
"Adobe is aware of reports that these vulnerabilities are being exploited in the wild in targeted attacks designed to trick Windows users into clicking on a malicious PDF file delivered in an email message," the company confirmed in its advisory.
"Adobe is in the process of working on a fix for these issues and will update this advisory when a date for the fix has been determined."