It was discovered that BIND, a DNS server, contains a race condition when processing zones updates in an authoritative server, either through dynamic DNS updates or incremental zone transfer . Such an update while processing a query could result in deadlock and denial of service. In addition, this security update addresses a defect related to the processing of new DNSSEC DS records by the caching resolver, which may lead to name resolution failures in the delegated zone. If DNSSEC validation is enabled, this issue can make domains ending in .COM unavailable when the DS record for .COM is added to the DNS root zone on March 31st, 2011. An unpatched server which is affected by this issue can be restarted, thus re-enabling resolution of .COM domains. This workaround applies to the version in oldstable, too. Configurations not using DNSSEC validations are not affected by this second issue.