Server Update Time: OpenSSH Vulnerability Disclosed

The OpenSSH team just released a security advisory about a vulnerability affecting both OpenSSH 6.2 and 6.3.

If you are not familiar with OpenSSH, it’s the software used by a large majority of servers and hosting providers to provide SFTP and SSH services. Any vulnerability discovered in OpenSSH could have a major impact to website owners, and the Internet in general.

The good news is that this vulnerability only affects newer versions of OpenSSH, which are not widely used yet. If you are using Ubuntu 13.10 or Fedora 19, you are likely vulnerable. All other Linux distributions appears to be safe. To double check, log into your server via SSH and type the following command:

# sshd -h
OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010

If you see OpenSSH_6.2 or OpenSSH_6.3, you know you are using the affected versions.

Remote Code Execution

The OpenSSH team explained the vulnerability in details in their advisory:

A memory corruption vulnerability exists in the post-authentication sshd process when an AES-GCM cipher(aes128-gcm@openssh.com or aes256-gcm@openssh.com) is selected during kex exchange.

If exploited, this vulnerability might permit code execution with the privileges of the authenticated user and may therefore allow bypassing restricted shell/command configurations.

When you read about code execution or bypassing restricting shell/command configurations, you know it is something important. So if you own a dedicated or virtual server, please update now!

If you have any questions, please email us, or leave us a comment below.