Vulnerability Note VU#915404

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 DNS Security Extensions (DNSSEC) signed Resource Record Sets (RRsets).

The specific impact of this vulnerability is slightly different depending on the type of DNS server involved. For recursive servers, queries for SIG records will trigger an assertion failure if more than one SIG(covered) RRset is returned. For authoritative servers, if a name server is serving a RFC 2535 DNSSEC zone and is queried for the SIG records where there are multiple SIG(covered) RRsets (e.g., a zone apex) then the name server daemon will trigger an assertion failure when it tries to construct the response.

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.

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 9.3.2-P1. Patches for this issue are also included in BIND versions 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.