This indicates an attempt to exploit a heap based buffer overflow vulnerability in F-Prot Antivirus.
A remote attacker could cause the F-Prot application to crash or execute arbitrary code with the privileges of the application, by sending a specially crafted CHM file to the victim.
F-Prot Antivirus version 4.6.6 and prior.
System compromise: remote code execution.
Update to the latest version of F-Prot Antivirus (4.6.7 or later).