BIND Dynamic Update DoS

Summary:

BIND denial of service (server crash) caused by receipt of a specific remote dynamic update message.

CVE:

CVE-2009-0696

CERT:

VU#725188

Posting date:

28 Jul 2009

Program Impacted:

BIND

Versions affected:

BIND 9 (all version)

Severity:

High

Exploitable:

remotely

Description:

Urgent: this exploit is public. Please upgrade immediately.

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).

Workarounds:

None.

(Some sites may have firewalls that can be configured with packet filtering techniques to prevent nsupdate messages from reaching their nameservers.)

Active exploits:

An active remote exploit is in wide circulation at this time.

Solution:

Upgrade BIND to one of 9.4.3-P3, 9.5.1-P3 or 9.6.1-P1. These versions can be downloaded from:

http://ftp.isc.org/isc/bind9/9.6.1-P1/bind-9.6.1-P1.tar.gz

http://ftp.isc.org/isc/bind9/9.5.1-P3/bind-9.5.1-P3.tar.gz

http://ftp.isc.org/isc/bind9/9.4.3-P3/bind-9.4.3-P3.tar.gz

Acknowledgment:

Matthias Urlichs for reporting the problem.
Tom Daly for methodical follow-on testing.

Revision History:

2009-07-28 Initial text
2009-07-29 Update to reflect Tom Daly's findings