Mentioned in the article is another finding, that the average lifetime of a Linux security bug in the wild is about five years...

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“Most serious” Linux privilege-escalation bug ever is under active exploit
Lurking in the kernel for nine years, flaw gives untrusted users unfettered root access.
Dan Goodin - 10/20/2016

A serious vulnerability that has been present for nine years in virtually all versions of the Linux operating system is under active exploit, according to researchers who are advising users to install a patch as soon as possible.

While CVE-2016-5195, as the bug is cataloged, amounts to a mere privilege-escalation vulnerability rather than a more serious code-execution vulnerability, there are several reasons many researchers are taking it extremely seriously. For one thing, it's not hard to develop exploits that work reliably. For another, the flaw is located in a section of the Linux kernel that's a part of virtually every distribution of the open-source OS released for almost a decade. What's more, researchers have discovered attack code that indicates the vulnerability is being actively and maliciously exploited in the wild.

"It's probably the most serious Linux local privilege escalation ever," Dan Rosenberg, a senior researcher at Azimuth Security, told Ars. "The nature of the vulnerability lends itself to extremely reliable exploitation. This vulnerability has been present for nine years, which is an extremely long period of time."

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http://arstechnica.com/security/2016/10/most-serious-linux-privilege-escalation-bug-ever-is-under-active-exploit/