Software Engineering Institute

The ISC security advisory states:

"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."

An attacker may cause the Bind server to stop processing all requests.

BIND 9.7.1 or 9.7.2 users should upgrade to BIND 9.7.3. Earlier versions are not vulnerable. BIND 9.5 is End of Life and is not supported by ISC. BIND 9.8 is not vulnerable.

The ISC advisory contains the following workaround:
"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."