librpc.dll in nsrexecd in EMC NetWorker before 7.5 SP4, 7.5.3.x before 7.5.3.5, and 7.6.x before 7.6.1.2 does not properly mitigate the possibility of a spoofed localhost source IP address, which allows remote attackers to (1) register or (2) unregister RPC services, and consequently cause a denial of service or obtain sensitive information from interprocess communication, via crafted UDP packets containing service commands.