diff --git a/impl/src/layer2/packet_structs.c b/impl/src/layer2/packet_structs.c
index ca11283..73bb469 100644
--- a/impl/src/layer2/packet_structs.c
+++ b/impl/src/layer2/packet_structs.c
@@ -33,13 +33,27 @@ size_t layer2_encode_packet_header(const layer2_packet_header_t *header, uint8_t
 }
 
 
-bool layer2_decode_packet_header(const uint8_t *encoded, layer2_packet_header_t *header)
+bool layer2_decode_packet_header(const uint8_t *encoded, size_t encoded_len, layer2_packet_header_t *header)
 {
+	// check if there are enough bytes for the minimum header size:
+	// - 1 byte packet info
+	// - 1 byte sequence numbers
+	// - 2 bytes source address
+	// - 2 bytes destination address
+	if(encoded_len < 6) {
+		return false;
+	}
+
 	header->msg_type = (encoded[0] >> 5) & 0x7;
 	header->tx_request = (encoded[0] & 0x10) != 0;
 	header->src_addr.length = (encoded[0] >> 2) & 0x3 + 1;
 	header->dst_addr.length = (encoded[0] >> 0) & 0x3 + 1;
 
+	// check for the actually needed size
+	if(encoded_len < (2 + 2*header->src_addr.length + 2*header->dst_addr.length)) {
+		return false;
+	}
+
 	header->tx_seq_nr = (encoded[1] >> 4) & 0xF;
 	header->tx_seq_nr = (encoded[1] >> 0) & 0xF;
 
diff --git a/impl/src/layer2/packet_structs.h b/impl/src/layer2/packet_structs.h
index e7429a7..82f42d4 100644
--- a/impl/src/layer2/packet_structs.h
+++ b/impl/src/layer2/packet_structs.h
@@ -19,8 +19,8 @@ typedef struct layer2_packet_header_s {
 	layer2_message_type_t msg_type; //!< message type
 	bool tx_request;                //!< transmission request (marks the end of the burst)
 
-	uint8_t tx_seq_nr;              //!< sequence number of this packet
-	uint8_t rx_seq_nr;              //!< sequence number expected next from he other side
+	uint8_t tx_seq_nr;              //!< sequence number (0 to 15) of this packet
+	uint8_t rx_seq_nr;              //!< sequence number (0 to 15) expected next from he other side
 
 	ham64_t src_addr;               //!< source HAM-64 address
 	ham64_t dst_addr;               //!< destination HAM-64 address
@@ -34,11 +34,12 @@ typedef struct layer2_packet_header_s {
 size_t layer2_encode_packet_header(const layer2_packet_header_t *header, uint8_t *encoded);
 
 /*!\brief Decode a layer2 packet header from the received form.
- * \param encoded  A byte array containing the received header.
- * \param header   The header structure where the decoded information is stored.
- * \returns        Whether the header was decoded successfully.
+ * \param encoded      A byte array containing the received header.
+ * \param encoded_len  Length (in bytes) of the given encoded data.
+ * \param header       The header structure where the decoded information is stored.
+ * \returns            Whether the header was decoded successfully.
  */
-bool layer2_decode_packet_header(const uint8_t *encoded, layer2_packet_header_t *header);
+bool layer2_decode_packet_header(const uint8_t *encoded, size_t encoded_len, layer2_packet_header_t *header);
 
 /* Data Packet Structs */