C++ memcpy - defective address - c++

Question

I have a vector that receives bytes from the network:
std:vector<unsigned char> data
I am trying to copy the address of the data into an unsigned char *[] array:
unsigned char *buffer = new unsigned char [1024*1024]
I am trying to loop through it to find a valid data packet that I am looking for. The sample code is below.
When I try to do memcpy to process the data I get an error saying defective address.
//process data
unsigned char * processPtr = NULL;
memcpy((void *) processPtr, hdr, sizeof(Header));
memcpy((void *) (processPtr + sizeof(Header)), (void *) ((unsigned char *) hdr + sizeof(Header))), hdr-> nubBytes);
Appreciate some help on this
header file:
typedef struct {
uint word;
int id;
int nubBytes;
}Header;
#define WORD 0xA345
unsigned char * buffer = new unsigned char[1024*1024];
Header *hdr;
int pktOffset;
cpp file:
Decode msg(std:vector<unsigned char> data, uint32_t bytesrcvd){
pktOffset = 0;
buffer = &data[0];
rcvBufOffSet += bytesRcvd;
numBytesInRecBuff += bytesRcvd;
hdr = (Header *)(& buffer[pktOffset])
if(hdr->word != WORD){
while(hdr->word != WORD && numBytesInRecBuff > 0)
pktOffset++;
numBytesInRecBuff--;
hdr = (Header *)(& Buffer[pktOffset])
}
if(hdr->word != WORD){
return;
}
else{
//process data
unsigned char * processPtr = NULL;
memcpy((void *) processPtr, hdr, sizeof(Header));
memcpy((void *) (processPtr + sizeof(Header)), (void *) ((unsigned char *) hdr + sizeof(Header))), hdr-> nubBytes);
processPacket((Header *)processPtr, unsigned char * (processPtr + + sizeof(Header)));
}
}
processPacket(Header * hdrPtr, unsigned char * dataPtr){
//further processing
}