The IPv6InterfaceInit() function contains a check for an invalid MTU. However, the function returns 0 (success) even if the invalid MTU is found (ipv6.c line ~851):

    if (ptr_device->mtu < MIN_IPV6_MTU)
        return 0;

This code should be returning a failure (-1), as the IPv6 initialization, object creations, etc. have not happened yet.