CAPEC Details
Name UDP Fragmentation
Likelyhood of attack Typical severity
Medium High
Summary An attacker may execute a UDP Fragmentation attack against a target server in an attempt to consume resources such as bandwidth and CPU. IP fragmentation occurs when an IP datagram is larger than the MTU of the route the datagram has to traverse. Typically the attacker will use large UDP packets over 1500 bytes of data which forces fragmentation as ethernet MTU is 1500 bytes. This attack is a variation on a typical UDP flood but it enables more network bandwidth to be consumed with fewer packets. Additionally it has the potential to consume server CPU resources and fill memory buffers associated with the processing and reassembling of fragmented packets.
Prerequisites This type of an attack requires the attacker to be able to generate fragmented IP traffic containing crafted data.
Solutions This attack may be mitigated by changing default cache sizes to be larger at the OS level. Additionally rules can be enforced to prune the cache with shorter timeouts for packet reassembly as the cache nears capacity.
Related Weaknesses
CWE ID Description
CWE-404 Improper Resource Shutdown or Release
CWE-770 Allocation of Resources Without Limits or Throttling
Related CAPECS
CAPEC ID Description
CAPEC-130 An adversary causes the target to allocate excessive resources to servicing the attackers' request, thereby reducing the resources available for legitimate services and degrading or denying services. Usually, this attack focuses on memory allocation, but any finite resource on the target could be the attacked, including bandwidth, processing cycles, or other resources. This attack does not attempt to force this allocation through a large number of requests (that would be Resource Depletion through Flooding) but instead uses one or a small number of requests that are carefully formatted to force the target to allocate excessive resources to service this request(s). Often this attack takes advantage of a bug in the target to cause the target to allocate resources vastly beyond what would be needed for a normal request.