The ESMTP inspection feature on Cisco Adaptive Security Appliances (ASA) 5500 series devices with software 8.2 through 8.5 allows remote attackers to cause a denial of service (CPU consumption) via an unspecified closing sequence, aka Bug ID CSCtt32565.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.