This indicates an attack attempt against a integer overflow vulnerability in Nullsoft Winamp.
The vulnerability is caused by an error when the CAF file parsing component handles a specially crafted CAF (Core Audio Format) file. It allows a remote attacker to execute arbitrary code.
Nullsoft Winamp version 5.55 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Upgrade to Nullsoft Winamp version 5.551: