int buffer_replace2(struct buffer *b, char *pos, char *end, const char *str, int len)
{
	int delta;

	delta = len - (end - pos);

	if (bi_end(b) + delta > b->data + b->size)
		return 0;  /* no space left */

	if (buffer_not_empty(b) &&
	    bi_end(b) + delta > bo_ptr(b) &&
	    bo_ptr(b) >= bi_end(b))
		return 0;  /* no space left before wrapping data */

	/* first, protect the end of the buffer */
	memmove(end + delta, end, bi_end(b) - end);

	/* now, copy str over pos */
	if (len)
		memcpy(pos, str, len);

	b->i += delta;

	if (buffer_empty(b))
		b->p = b->data;

	return delta;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.