Original URL: http://www.theregister.co.uk/2009/07/29/bind_flaw/

BIND crash bug prompts urgent update call

Master server flaw could break the interwebs

By John Leyden

Posted in Security, 29th July 2009 12:20 GMT

A vulnerability in BIND creates a means for miscreants to crash vulnerable Domain Name System servers, posing a threat to overall internet stability as a result.

Exploits targeted at BIND (Berkeley Internet Name Domain Server) version 9 are already in circulation, warns the Internet Software Consortium, the group which develops the software. ISC urges sys admins to upgrade immediately, to defend against the "high risk" bug.

Sys admins are urged to upgrade BIND servers to versions 9.4.3-P3, 9.5.1-P3 or 9.6.1-P1 of the software, which defend against the flaw.

The vulnerability involves BIND servers that act as a master (slave systems are unaffected) and involves problems in dealing with malformed update messages, which can used to cause a server to crash, as explained in a security alert by ISC here.

Receipt of a specially-crafted dynamic update message to a zone for which the server is the master may cause BIND 9 servers to exit. Testing indicates that the attack packet has to be formulated against a zone for which that machine is a master. Launching the attack against slave zones does not trigger the assert.

BIND is used on a great majority of DNS servers on the Internet. DNS maps between easy-to-remember domain names, understood by humans, and their corresponding numerical IP addresses, needed by computers. Simply put, the system can be compared to a phone book for the internet.

Screwing with this system creates a means to possibly derail surfing and email delivery, among many other undesirable effects. ®