evutil_found_ifaddr(const struct sockaddr *sa)
{
	const char ZEROES[] = "\x00\x00\x00\x00\x00\x00\x00\x00"
	    "\x00\x00\x00\x00\x00\x00\x00\x00";

	if (sa->sa_family == AF_INET) {
		const struct sockaddr_in *sin = (struct sockaddr_in *)sa;
		ev_uint32_t addr = ntohl(sin->sin_addr.s_addr);
		if (addr == 0 ||
		    EVUTIL_V4ADDR_IS_LOCALHOST(addr) ||
		    EVUTIL_V4ADDR_IS_CLASSD(addr)) {
			/* Not actually a usable external address. */
		} else {
			event_debug(("Detected an IPv4 interface"));
			had_ipv4_address = 1;
		}
	} else if (sa->sa_family == AF_INET6) {
		const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa;
		const unsigned char *addr =
		    (unsigned char*)sin6->sin6_addr.s6_addr;
		if (!memcmp(addr, ZEROES, 8) ||
		    ((addr[0] & 0xfe) == 0xfc) ||
		    (addr[0] == 0xfe && (addr[1] & 0xc0) == 0x80) ||
		    (addr[0] == 0xfe && (addr[1] & 0xc0) == 0xc0) ||
		    (addr[0] == 0xff)) {
			/* This is a reserved, ipv4compat, ipv4map, loopback,
			 * link-local, multicast, or unspecified address. */
		} else {
			event_debug(("Detected an IPv6 interface"));
			had_ipv6_address = 1;
		}
	}
}

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.