The opus_packet_get_samples_per_frame function in client in Mumble 1.2.4 and the 1.2.3 pre-release snapshots allows remote attackers to cause a denial of service (crash) via a crafted length prefix value, which triggers a NULL pointer dereference or a heap-based buffer over-read (aka "out-of-bounds array access").
Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary.