How To Protect Your Server Against the Dirty COW Linux Vulnerability

Introduction : On October 19, 2016, a privilege escalation vulnerability in the Linux kernel was disclosed. The bug is nicknamed Dirty COW because the underlying issue was a race condition in the way kernel handles copy-on-write (COW). Dirty COW has existed for a long time at least since 2007, with kernel version 2.6.22 so the vast majority of servers are at risk.

Exploiting this bug means that a regular, unprivileged user on your server can gain write access to any file they can read, and can therefore increase their privileges on the system. More information can be found on CVE-2016-5195 from Canonical, Red Hat, and Debian.

Check Vulnerability :


To find out if your server is affected, check your kernel version.

# uname -rv

You’ll see output like this:
4.4.0-42-generic #62-Ubuntu SMP Fri Oct 7 23:11:45 UTC 2016

If your version is earlier than the following, you are affected:

  • 4.8.0-26.28 for Ubuntu 16.10
  • 4.4.0-45.66 for Ubuntu 16.04 LTS
  • 3.13.0-100.147 for Ubuntu 14.04 LTS
  • 3.2.0-113.155 for Ubuntu 12.04 LTS
  • 3.16.36-1+deb8u2 for Debian 8
  • 3.2.82-1 for Debian 7
  • 4.7.8-1 for Debian unstable

If you’re on CentOS, you can use this script provided by RedHat to test your server’s vulnerability. To do so, first download the script.


Then run it with bash.

# bash

If you’re vulnerable, you’ll see output like this:

Your kernel is 3.10.0-327.36.1.el7.x86_64 which IS vulnerable.
Red Hat recommends that you update your kernel. Alternatively, you can apply partial
mitigation described at .

Fix Vulnerability

Fortunately, applying the fix is straightforward: update your system and reboot your server.


Update and upgrade your packages using apt-get.

# sudo apt-get update && sudo apt-get dist-upgrade

You’ll need to reboot your server to apply the changes.

# sudo reboot


At this time, we’re still waiting for Red Hat to release a patch. This tutorial will be updated with instructions on how to secure your CentOS server as soon as possible. In the interim, you can use this workaround from the Red Hat bug tracker.


Make sure to update your Linux servers to stay protected from this privilege escalation bug.

Virtualizor 2.8.7 Launched (Release Branch) (Patch 5)


The Virtualizor Team has released Virtualizor 2.8.7 (Release Branch) (Patch 5)
This version introduces features like Cloning VMs, a new VPS Management Wizard, improved migration for KVM, XEN and fixes some bugs.

The change log for the 2.8.7 is here :

Virtualizor supports OpenVZ, Xen, XenServer and Linux-KVM on CentOS and Ubuntu and they all can be managed from the Master. We are adding more features and if you have any suggestions, do let us know. We hope you enjoy this version of Virtualizor. LXC is available only for CentOS 7.x.

The Virtualizor Team

Updated WHMCS Module V2 (2.0.7)


We have updated the WHMCS Module V2, please download the new files and update the module.

You can download the new module from the following link :

This update has the following changes :

1) On WHMCS 7, users were facing while setting module setting. Plans were not loading under module settings tab for product. This is fixed.

Virtualizor Team.