A potentially serious denial-of-service (DoS) vulnerability was patched this week by the Internet Systems Consortium (ISC) in the BIND DNS software.
The flaw, tracked as CVE-2017-3135, affects BIND 9.8.8, all 9.9 releases since 9.9.3, all 9.10 releases, and all 9.11 releases.
In the case of servers with specific configurations, the vulnerability is remotely exploitable and rated as “high severity” with a CVSS score of 7.5.
“Under some conditions when using both DNS64 and RPZ [Response Policy Zones] to rewrite query responses, query processing can resume in an inconsistent state leading to either an INSIST assertion failure or an attempt to read through a NULL pointer,” ISC said in its advisory.
“Servers utilizing both DNS64 and RPZ are potentially susceptible to encountering this condition. When this condition occurs, it will result in either an INSIST assertion failure (and subsequent abort) or an attempt to read through a NULL pointer. On most platforms a NULL pointer read leads to a segmentation fault (SEGFAULT), which causes the process to be terminated,” ISC added.
Servers that don’t use RPZ and DNS64 at the same time are not affected by the security hole.
The vulnerability, reported by Ramesh Damodaran and Aliaksandr Shubnik of Infoblox, has been patched with the release of versions 9.9.9-P6, 9.10.4-P6 and 9.11.0-P3. Users have been advised to update their installations, but removing DNS64 or RPZ from the configuration or restricting the contents of the policy zone are considered a workaround.
The flaw was disclosed on Wednesday, but advance notifications were sent out on February 1. Linux distributions, most of which have classified this as a medium severity issue, are working on releasing patches.
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Related: High Severity DoS Flaw Patched in BIND