The Internet Systems Consortium (ISC) and US-CERT have issued a high severity vulnerability warning, discovered by Neustar, which affects BIND, the most widely used DNS software on the Internet. Successful exploitation could enable attacker to cause Bind servers to stop processing all requests.

According to the ISC’s disclosure, "When an authoritative server processes a successful IXFR transfer or a dynamic update, there is a small window of time during which the IXFR/update coupled with a query may cause a deadlock to occur. This deadlock will cause the server to stop processing all requests. A high query rate and/or a high update rate will increase the probability of this condition."

As far as a workaround, the ISC advisory suggests the following: "Depending on your performance requirements, a work-around may be available. ISC was not able to reproduce this defect in 9.7.2 using -n 1, which causes named to use only one worker thread, thus avoiding the deadlock. If your server is powerful enough to serve your data with a single processor, this option may be fast to implement until you have time to perform an upgrade."

There have been no active exploits known, and versions 9.7.1-9.7.2-P3 versions of BIND are affected. US-CERT encourages users and administrators using the effected versions of BIND to upgrade to BIND 9.7.3.

The vulnerability has Common Vulnerability Scoring System (CVSS) score of 7.1.

Related Technical Reading: Introduction to Security for Smart Object Network Devices

Additional Information:

Program Impacted: BIND, Versions 9.7.1-9.7.2-P3

Posting date: February 22, 2011

CVE: CVE-2011-0414

CERT: VU#559980

Severity: High

Exploitable: Remotely