NeKernal is a free and open-source operating system stack. Version 0.0.2 has a 1-byte heap overflow in `rt_copy_memory`, which unconditionally wrote a null terminator at `dst[len]`. When `len` equals the size of the destination buffer (256 bytes), that extra `'\0'` write overruns the buffer by one byte. To avoid breaking existing callers or changing the public API, the patch in commit fb7b7f658327f659c6a6da1af151cb389c2ca4ee takes a minimal approach: it simply removes the overflow-causing line without adding bounds checks or altering the function signature.
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().