static char *php_gethostbyaddr(char *ip)
{
#if HAVE_IPV6 && HAVE_INET_PTON
	struct in6_addr addr6;
#endif
	struct in_addr addr;
	struct hostent *hp;

#if HAVE_IPV6 && HAVE_INET_PTON
	if (inet_pton(AF_INET6, ip, &addr6)) {
		hp = gethostbyaddr((char *) &addr6, sizeof(addr6), AF_INET6);
	} else if (inet_pton(AF_INET, ip, &addr)) {
		hp = gethostbyaddr((char *) &addr, sizeof(addr), AF_INET);
	} else {
		return NULL;
	}
#else
	addr.s_addr = inet_addr(ip);

	if (addr.s_addr == -1) {
		return NULL;
	}

	hp = gethostbyaddr((char *) &addr, sizeof(addr), AF_INET);
#endif

	if (!hp || hp->h_name == NULL || hp->h_name[0] == '\0') {
		return estrdup(ip);
	}

	return estrdup(hp->h_name);
}

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.