Security Advisory: Server Lockup Upon IXFR or DDNS Update Combined with High Query Rate
larissas at isc.org
Tue Feb 22 20:54:42 UTC 2011
Internet Systems Consortium Security
Title: Server Lockup Upon IXFR or DDNS Update Combined with High Query Rate
CVSS: 7.1 (AV:N/AC:M/Au:N/C:N/I:N/A:C)
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Posting date: 2011-02-22
Program Impacted: BIND
Versions affected: 9.7.1-9.7.2-P3
Description and Impact:
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
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.
Active exploits: None known, but a description of the issue is available
in the release notes for BIND 9.6.3 and 9.7.3.
Solution: 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-R?, 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.
Questions regarding this advisory or ISC's Support services should be
sent to bind9-bugs at isc.org <mailto:bind9-bugs at isc.org>
For more information on ISC's support, consulting, training, and other
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