In libavformat/rmdec.c in FFmpeg 3.3.3, a DoS in ivr_read_header() due to lack of an EOF (End of File) check might cause huge CPU consumption. When a crafted IVR file, which claims a large "len" field in the header but does not contain sufficient backing data, is provided, the first type==4 loop would consume huge CPU resources, since there is no EOF check inside the loop.