Software Engineering Institute

mDNS uses IP multicast with DNS to provide the functionality of a DNS server for service discovery in networks that do not have a DNS server. mDNSResponder uses Multicast DNS Service Discovery for service discovery on the local network segment, and Unicast DNS Service Discovery for service discovery outside of the local network.

Bonjour provides zero-confirguation networking for Apple OS X. mDNSResponder is included as a part of Bonjour and runs as a system service. mDNSResponder is a included in OS X and Apple TV.

mDNSResponder contains a buffer overflow vulnerability. This vulnerability occurs in the UPnP IGD (Internet Gateway Device Standardized Device Control Protocol) code that is used to create dynamic port mappings in consumer routers.

Note that an attacker would need to be able to send multicast packets to a vulnerable system to exploit this vulnerability.

An attacker may be able to execute arbitrary code with root privileges, or create a denial of service condition.

Update
Apple has released Security Update 2007-005 to address this issue. Users are encouraged to apply these updates as soon as possible.

Restrict access

Until updates can be applied, creating a firewall rule to restrict access to 5353/udp and 1900/udp may mitigate this vulnerability. See the Apple Support document Creating an Advanced IP Firewall Rule for more information on how to create firewall rules. Note that blocking these ports may cause applications that rely on Bonjour to fail.