The Trend Micro scan engine before 8.320 for Windows and before 8.150 on HP-UX and AIX, as used in Trend Micro PC Cillin - Internet Security 2006, Office Scan 7.3, and Server Protect 5.58, allows remote attackers to cause a denial of service (CPU consumption and system hang) via a malformed RAR archive with an Archive Header section with the head_size and pack_size fields set to zero, which triggers an infinite loop.