A heap buffer overflow in the TFTP receiving code allows for DoS or arbitrary code execution in libcurl versions 7.19.4 through 7.64.1.
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().
The product writes data past the end, or before the beginning, of the intended buffer.