BIND 9 dynamic update DoS vulnerability

A DoS vulnerability has been discovered in BIND 9 and an active remote exploit is in wide circulation at this time.

Receipt of a specially-crafted dynamic update message to a zone for which the server is the master may cause BIND 9 servers to exit. Testing indicates that the attack packet has to be formulated against a zone for which that machine is a master. Launching the attack against slave zones does not trigger the assert.

This vulnerability affects all servers that are masters for one or more zones – it is not limited to those that are configured to allow dynamic updates. Access controls will not provide an effective workaround.

dns_db_findrdataset() fails when the prerequisite section of the dynamic update message contains a record of type “ANY” and where at least one RRset for this FQDN exists on the server.

db.c:659: REQUIRE(type != ((dns_rdatatype_t)dns_rdatatype_any)) failed
exiting (due to assertion failure).

At the moment there is no workaround. Some sites may have firewalls that can be configured with packet filtering techniques to prevent nsupdate messages from reaching their nameservers.

Upgrade BIND to one of 9.4.3-P3, 9.5.1-P3 or 9.6.1-P1:

  • bind-9.6.1-P1.tar.gz
  • bind-9.5.1-P3.tar.gz
  • bind-9.4.3-P3.tar.gz



Share this