Stack-based buffer overflow in Quick Heal Internet Security 10.1.0.316 and earlier, Total Security 10.1.0.316 and earlier, and AntiVirus Pro 10.1.0.316 and earlier on OS X allows remote attackers to execute arbitrary code via a crafted LC_UNIXTHREAD.cmdsize field in a Mach-O file that is mishandled during a Security Scan (aka Custom Scan) operation.