Security Alert: DNS Security Vulnerability

by Cory Wright

Earlier this week Dan Kaminsky announced a major security vulnerability in the 25 year old DNS protocol. DNS is used to translate human readable addresses such as into IP addresses that computers use to talk to one another across networks such as the Internet. Kaminsky, a security researcher with IO Active, stressed that the issue was in the design of DNS and therefore affected software across all operating systems.

Of course, the most popular DNS software on Linux is BIND, which is shipped with almost every distribution. Kaminsky worked with many major software vendors to ensure that security updates were available simultaneously. Debian, Red Hat, Ubuntu, and many other distributions have already provided updated versions of BIND. One thing to note is that if you are running BIND 8 servers anywhere you should take this opportunity to upgrade to BIND 9. The BIND 8 codebase is no longer supported, and security updates are not available.

Even though this is a protocol issue, some software and services are not affected. Systems using Dan Bernstein's djbdns package are not vulnerable to this type of attack. Users of PowerDNS and OpenDNS are also not susceptible. Kaminsky has provided a tool on his website that you can use to check your DNS service.

Although this is a major security issue, the details of the exploit have not yet been released by Kaminsky. The coordinated effort with vendors gave them a chance to patch their systems before Kaminsky takes the stage at the annual Black Hat security conference next month in Las Vegas. It is expected that he will discuss the vulnerability in depth at the conference, at which point exploits are sure to begin appearing. An Executive Overview (PDF) of the vulnerability is available, along with the CERT Advisory. A list of the affected systems is given near the bottom of the advisory.

If you manage DNS services please take time to update your system with the latest software available.