diff --git a/client.cpp b/client.cpp
index c82a0b7..c3a47cf 100644
--- a/client.cpp
+++ b/client.cpp
@@ -310,13 +310,16 @@ bool Client::bufferToMqttPackets(std::vector<MqttPacket> &packetQueueIn, Client_
         // Determine the packet length by decoding the variable length
         int remaining_length_i = 1; // index of 'remaining length' field is one after start.
         uint fixed_header_length = 1;
-        int multiplier = 1;
-        uint packet_length = 0;
+        size_t multiplier = 1;
+        size_t packet_length = 0;
         unsigned char encodedByte = 0;
         do
         {
             fixed_header_length++;
 
+            if (fixed_header_length > 5)
+                throw ProtocolError("Packet signifies more than 5 bytes in variable length header. Invalid.");
+
             // This happens when you only don't have all the bytes that specify the remaining length.
             if (fixed_header_length > readbuf.usedBytes())
                 return false;
@@ -335,6 +338,11 @@ bool Client::bufferToMqttPackets(std::vector<MqttPacket> &packetQueueIn, Client_
             throw ProtocolError("An unauthenticated client sends a packet of 1 MB or bigger? Probably it's just random bytes.");
         }
 
+        if (packet_length > ABSOLUTE_MAX_PACKET_SIZE)
+        {
+            throw ProtocolError("A client sends a packet claiming to be bigger than the maximum MQTT allows.");
+        }
+
         if (packet_length <= readbuf.usedBytes())
         {
             MqttPacket packet(readbuf, packet_length, fixed_header_length, sender);
diff --git a/mqttpacket.cpp b/mqttpacket.cpp
index fa58114..93f7886 100644
--- a/mqttpacket.cpp
+++ b/mqttpacket.cpp
@@ -17,6 +17,7 @@ MqttPacket::MqttPacket(CirBuf &buf, size_t packet_len, size_t fixed_header_lengt
     fixed_header_length(fixed_header_length),
     sender(sender)
 {
+    assert(packet_len > 0);
     buf.read(bites.data(), packet_len);
 
     first_byte = bites[0];
@@ -116,6 +117,9 @@ MqttPacket::MqttPacket(const PubAck &pubAck) :
 
 void MqttPacket::handle()
 {
+    if (packetType == PacketType::Reserved)
+        throw ProtocolError("Packet type 0 specified, which is reserved and invalid.");
+
     if (packetType != PacketType::CONNECT)
     {
         if (!sender->getAuthenticated())