The FWDRV.SYS driver in Kerio Personal Firewall 4.1.1 and earlier allows remote attackers to cause a denial of service (CPU consumption and system freeze from infinite loop) via a (1) TCP, (2) UDP, or (3) ICMP packet with a zero length IP Option field.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17992
http://www.kerio.com/security_advisory.html
http://www.eeye.com/html/research/advisories/AD20041109.html