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ISC Bind 9 IXFR or DDNS update combined with high query rate DoS vulnerability

Vulnerability Note VU#559980

Original Release Date: 2011-02-22 | Last Revised: 2011-02-23


A denial-of-service condition exists in certain cases when an ISC Bind server processes a IXFR transfer or dynamic update.


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."

Vendor Information


Internet Systems Consortium Affected

Notified:  January 24, 2011 Updated: February 23, 2011



Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

CVSS Metrics

Group Score Vector



Thanks to ISC for reporting this vulnerability.

This document was written by Jared Allar.

Other Information

CVE IDs: CVE-2011-0414
Severity Metric: 4.50
Date Public: 2011-02-22
Date First Published: 2011-02-22
Date Last Updated: 2011-02-23 11:36 UTC
Document Revision: 13

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