The needSamples method in AudioOutputSpeech.cpp in the client in Mumble 1.2.4 and the 1.2.3 pre-release snapshots, Mumble for iOS 1.1 through 1.2.2, and MumbleKit before commit fd190328a9b24d37382b269a5674b0c0c7a7e36d does not check the return value of the opus_decode_float function, which allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted Opus voice packet, which triggers an error in opus_decode_float, a conversion of a negative integer to an unsigned integer, and a heap-based buffer over-read and over-write.