Microsoft has updated the following KB article:
A PXE enabled Distribution Point that uses a self-signed certificate will generate many files in System Center 2012 Configuration Manager
A PXE enabled Distribution Point will generate a number of files under C:\ProgramData\Microsoft\Crypto\RSA\S-1-5-18 for each PXE request that it services on the network. This occurs whether the device sending the PXE request has a Task Sequence deployed to it or not. The generation of files will continue and may consume available hard disk space.