Mitigating the Dirty Cow vulnerability in CentOS, RedHat, Ubuntu, Debian and Opensuse

How to fix Dirty Cow vulnerability in CentOS, RedHat, Ubuntu, Debian, CloudLinux and OpenSuse Linux servers

Dirty COW vulnerability was first discovered a decade ago and has been present in Linux kernel versions from 2.6.22, which was released in 2007.

But the vulnerability gained attention only recently when hackers started exploiting it. This has led to the release of this bug as CVE-2016-5195 on October 19th, 2016.
What is Dirty Cow vulnerability (CVE-2016-5195)?

CVE-2016-5195 aka “Dirty COW vulnerability” involves a privilege escalation exploit which affects the way memory operations are handled.

Since the feature that is affected by this bug is the copy-on-write (COW) mechanism in Linux kernel for managing ‘dirty’ memory pages, this vulnerability is termed ‘Dirty COW’.

Misusing this flaw in kernel, an unprivileged local user can escalate his privileges in the system and thus gain write access on read-only memory updates.

Using this privilege escalation, local users can write to any file that they can read. Any malicious application or user can thus tamper with critical read-only root-owned files.
Is Dirty Cow vulnerability (CVE-2016-5195) critical?

Dirty COW vulnerability affects the Linux kernel. Most open-source operating systems such as RedHat, Ubuntu, Fedora, Debian, etc. are based over Linux kernel.

As a result, this vulnerability is a ‘High’ priority one as it can affect a huge percentage of servers running over Linux and Android kernels.

CVE-2016-5195 exploit can be misused by malicious users who are provided with shell access in Linux servers. They can gain root access and attack other users.

When combined with other attacks such as SQL injection, this privilege escalation attack can even mess up the entire data in these servers, which makes it a critical one.
Are you servers affected by Dirty Cow exploit?

If your server or VM or container is hosted with any of these OS versions, then they are vulnerable:

Red Hat Enterprise Linux 7.x, 6.x and 5.x

CentOS Linux 7.x, 6.x and 5.x

Debian Linux wheezy, jessie, stretch and sid

Ubuntu Linux precise (LTS 12.04), trusty, xenial (LTS 16.04), yakkety and vivid/ubuntu-core

SUSE Linux Enterprise 11 and 12

For more information about mitigating yourself against Dirty cow, please see:

How to fix Dirty Cow vulnerability in CentOS, RedHat, Ubuntu, Debian, CloudLinux and OpenSuse Linux servers

Credit to Reeshma Mathews from bobcares.com for this

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