Race condition in the cut-through proxy feature in Cisco Firewall Services Module (FWSM) Software 3.x before 3.2(28) and 4.x before 4.1(15) allows remote attackers to cause a denial of service (device reload) via certain matching traffic, aka Bug ID CSCuj16824.
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140219-fwsm