A heap-based buffer overflow was found in the SDHCI device emulation of QEMU. The bug is triggered when both `s->data_count` and the size of `s->fifo_buffer` are set to 0x200, leading to an out-of-bound access. A malicious guest could use this flaw to crash the QEMU process on the host, resulting in a denial of service condition.
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().