Vulnerability Note VU#697164

The Berkeley Internet Name Domain (BIND) is a popular Domain Name System (DNS) implementation from Internet Systems Consortium (ISC). A flaw exists in the way that some versions of BIND handle recursive queries. It is possible for a remote attacker to trigger an INSIST failure by sending enough recursive queries that the response to the query arrives after all the clients looking for the response have left the recursion queue.

This vulnerability affects BIND 9.3.x versions 9.3.0, 9.3.1, 9.3.2, 9.3.3b, and 9.3.3rc1, and BIND 9.4.x versions 9.4.0a1, 9.4.0a2, 9.4.0a3, 9.4.0a4, 9.4.0a5, 9.4.0a6, and 9.4.0b1.

Note that although BIND versions 9.2.x also contain the underlying flaw that causes this vulnerability, ISC reports that the vulnerability is not exposed by these versions. Nonetheless, ISC has provided a patch for these versions as well.

A remote attacker may be able to cause the name server daemon to crash, thereby causing a denial of service for DNS operations.

Apply a patch from the vendor

Patches have been released in response to this issue. Please see the Systems Affected section of this document.

Upgrade

Users who compile their own versions of BIND from the original ISC source code are encouraged to upgrade to BIND 9.2.6-P1 or BIND 9.3.2-P1 as appropriate. Patches for this issue are also included in BIND versions 9.2.7rc2, 9.3.3rc2, and 9.4.0b2. Patched versions of the software are available from the BIND download page.

Restrict Access

Administrators, particularly those who are unable to apply a patch, can limit exposure to this vulnerability by restricting sources that can ask for recursion.