BIND: Server Lockup Upon IXFR or DDNS Update Combined with High Query Rate
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.
CVSS Score: 7.1 (AV:N/AC:M/Au:N/C:N/I:N/A:C)
For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2
Depending on your performance requirements, a work-around may be available. ISC was not able to reproduce this defect in 9.7.2 using -n1, 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.
If you run BIND 9.7.1 or 9.7.2, upgrade to BIND 9.7.3. Earlier versions are not vulnerable. If you run BIND 9.6.x, 9.6-ESV-Rx, or 9.4-ESV-R4, you do not need to upgrade.
BIND 9.5 is End of Life and is not supported by ISC. BIND 9.8 is not vulnerable.
Credits: Thank you to Neustar for finding the initial defect and JPRS for further testing and analysis.
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ISC Security Vulnerability Disclosure Policy: Details of our current security advisory policy and practice can be found here: https://www.isc.org/security-vulnerability-disclosure-policy
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