DarkFiber Consulting – IT Managed Services

DNS Cache Poisoning Public Exploit Code Available

July 25th, 2008 . by DarkFiber Consulting

DarkFiber Consulting is aware of publicly available exploit code for a cache poisoning vulnerability in common DNS implementations. Exploitation of this vulnerability may allow an attacker to cause a nameserver’s clients to contact the incorrect, and possibly malicious hosts for particular services. As a result, web traffic, email and other important network data could be redirected to systems under the attacker’s control.

DarkFiber Consulting strongly urges administrators to patch affected systems immediately. Please review the following DarkFiber Consulting documents for further details:

DarkFiber Consulting will provide additional information as it becomes available.

NAT/PAT Affects DNS Cache Poisoning Mitigation

July 23rd, 2008 . by DarkFiber Consulting

DarkFiber Consulting released a Current Activity entry and a Vulnerability Note on July 8, 2008 regarding deficiencies in DNS implementations. These deficiencies could leave an affected system vulnerable to cache poisoning. Technical details regarding this vulnerability have been posted to public websites. Attackers could use these details to construct exploit code. Users are encouraged to patch systems or apply workarounds immediately.

A number of patches implement source port randomization in the name server as a way to reduce the practicality of cache poisoning attacks. Administrators should be aware that in infrastructures where nameservers exist behind Network Address Translation (NAT) and Port Address Translation (PAT) devices, port randomization in the nameserver may be overwritten by the NAT/PAT device and a sequential port address could be allocated. This may weaken the protection offered by source port randomization in the nameserver.

DarkFiber Consulting encourages users to consider one of the following workarounds:

  • Place the nameserver outside of the NAT/PAT device in the network infrastructure.
  • Configure the NAT/PAT device to perform source port randomization.
  • Configure the NAT/PAT device to preserve the source port assigned by the nameserver.

Additional information can be found in DarkFiber Consulting Vulnerability Note VU#800113.

More information will be provided as it becomes available.