diff --git a/subsys/mgmt/osdp/src/osdp_cp.c b/subsys/mgmt/osdp/src/osdp_cp.c
index 3c8cfc2e8cc..e21747821de 100644
--- a/subsys/mgmt/osdp/src/osdp_cp.c
+++ b/subsys/mgmt/osdp/src/osdp_cp.c
@@ -80,6 +80,12 @@ int osdp_extract_address(int *address)
 	return (pd_offset == CONFIG_OSDP_NUM_CONNECTED_PD) ? 0 : -1;
 }
 
+static inline void assert_buf_len(int need, int have)
+{
+	__ASSERT(need < have, "OOM at build command: need:%d have:%d",
+		 need, have);
+}
+
 static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 {
 	struct osdp_cmd *cmd = NULL;
@@ -97,45 +103,50 @@ static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 
 	switch (pd->cmd_id) {
 	case CMD_POLL:
-		__fallthrough;
+		assert_buf_len(CMD_POLL_LEN, max_len);
+		buf[len++] = pd->cmd_id;
+		ret = 0;
+		break;
 	case CMD_LSTAT:
-		__fallthrough;
+		assert_buf_len(CMD_LSTAT_LEN, max_len);
+		buf[len++] = pd->cmd_id;
+		ret = 0;
+		break;
 	case CMD_ISTAT:
-		__fallthrough;
+		assert_buf_len(CMD_ISTAT_LEN, max_len);
+		buf[len++] = pd->cmd_id;
+		ret = 0;
+		break;
 	case CMD_OSTAT:
-		__fallthrough;
+		assert_buf_len(CMD_OSTAT_LEN, max_len);
+		buf[len++] = pd->cmd_id;
+		ret = 0;
+		break;
 	case CMD_RSTAT:
+		assert_buf_len(CMD_RSTAT_LEN, max_len);
 		buf[len++] = pd->cmd_id;
 		ret = 0;
 		break;
 	case CMD_ID:
-		if (max_len < CMD_ID_LEN) {
-			break;
-		}
+		assert_buf_len(CMD_ID_LEN, max_len);
 		buf[len++] = pd->cmd_id;
 		buf[len++] = 0x00;
 		ret = 0;
 		break;
 	case CMD_CAP:
-		if (max_len < CMD_CAP_LEN) {
-			break;
-		}
+		assert_buf_len(CMD_CAP_LEN, max_len);
 		buf[len++] = pd->cmd_id;
 		buf[len++] = 0x00;
 		ret = 0;
 		break;
 	case CMD_DIAG:
-		if (max_len < CMD_DIAG_LEN) {
-			break;
-		}
+		assert_buf_len(CMD_DIAG_LEN, max_len);
 		buf[len++] = pd->cmd_id;
 		buf[len++] = 0x00;
 		ret = 0;
 		break;
 	case CMD_OUT:
-		if (max_len < CMD_OUT_LEN) {
-			break;
-		}
+		assert_buf_len(CMD_OUT_LEN, max_len);
 		cmd = (struct osdp_cmd *)pd->cmd_data;
 		buf[len++] = pd->cmd_id;
 		buf[len++] = cmd->output.output_no;
@@ -145,9 +156,7 @@ static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		ret = 0;
 		break;
 	case CMD_LED:
-		if (max_len < CMD_LED_LEN) {
-			break;
-		}
+		assert_buf_len(CMD_LED_LEN, max_len);
 		cmd = (struct osdp_cmd *)pd->cmd_data;
 		buf[len++] = pd->cmd_id;
 		buf[len++] = cmd->led.reader;
@@ -169,9 +178,7 @@ static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		ret = 0;
 		break;
 	case CMD_BUZ:
-		if (max_len < CMD_BUZ_LEN) {
-			break;
-		}
+		assert_buf_len(CMD_BUZ_LEN, max_len);
 		cmd = (struct osdp_cmd *)pd->cmd_data;
 		buf[len++] = pd->cmd_id;
 		buf[len++] = cmd->buzzer.reader;
@@ -183,9 +190,7 @@ static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		break;
 	case CMD_TEXT:
 		cmd = (struct osdp_cmd *)pd->cmd_data;
-		if (max_len < (CMD_TEXT_LEN + cmd->text.length)) {
-			break;
-		}
+		assert_buf_len(CMD_TEXT_LEN + cmd->text.length, max_len);
 		buf[len++] = pd->cmd_id;
 		buf[len++] = cmd->text.reader;
 		buf[len++] = cmd->text.control_code;
@@ -199,9 +204,7 @@ static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		ret = 0;
 		break;
 	case CMD_COMSET:
-		if (max_len < CMD_COMSET_LEN) {
-			break;
-		}
+		assert_buf_len(CMD_COMSET_LEN, max_len);
 		cmd = (struct osdp_cmd *)pd->cmd_data;
 		buf[len++] = pd->cmd_id;
 		buf[len++] = cmd->comset.address;
@@ -217,9 +220,7 @@ static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 			LOG_ERR("Cannot perform KEYSET without SC!");
 			return OSDP_CP_ERR_GENERIC;
 		}
-		if (max_len < CMD_KEYSET_LEN) {
-			break;
-		}
+		assert_buf_len(CMD_KEYSET_LEN, max_len);
 		buf[len++] = pd->cmd_id;
 		buf[len++] = 1;  /* key type (1: SCBK) */
 		buf[len++] = 16; /* key length in bytes */
@@ -228,7 +229,8 @@ static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		ret = 0;
 		break;
 	case CMD_CHLNG:
-		if (smb == NULL || max_len < CMD_CHLNG_LEN) {
+		assert_buf_len(CMD_CHLNG_LEN, max_len);
+		if (smb == NULL) {
 			break;
 		}
 		osdp_fill_random(pd->sc.cp_random, 8);
@@ -242,7 +244,8 @@ static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		ret = 0;
 		break;
 	case CMD_SCRYPT:
-		if (smb == NULL || max_len < CMD_SCRYPT_LEN) {
+		assert_buf_len(CMD_SCRYPT_LEN, max_len);
+		if (smb == NULL) {
 			break;
 		}
 		osdp_compute_cp_cryptogram(pd);
@@ -489,6 +492,11 @@ static int cp_decode_response(struct osdp_pd *pd, uint8_t *buf, int len)
 		return OSDP_CP_ERR_UNKNOWN;
 	}
 
+	if (ret != OSDP_CP_ERR_NONE) {
+		LOG_ERR("Failed to decode response: REPLY(%02x) for CMD(%02x)",
+			pd->cmd_id, pd->reply_id);
+	}
+
 	if (pd->cmd_id != CMD_POLL) {
 		LOG_DBG("CMD(%02x) REPLY(%02x)", pd->cmd_id, pd->reply_id);
 	}
diff --git a/subsys/mgmt/osdp/src/osdp_pd.c b/subsys/mgmt/osdp/src/osdp_pd.c
index 228cf525f4c..f28f345ea19 100644
--- a/subsys/mgmt/osdp/src/osdp_pd.c
+++ b/subsys/mgmt/osdp/src/osdp_pd.c
@@ -299,7 +299,6 @@ static int pd_decode_command(struct osdp_pd *pd, uint8_t *buf, int len)
 #ifdef CONFIG_OSDP_SC_ENABLED
 	case CMD_KEYSET:
 		if (len != CMD_KEYSET_DATA_LEN) {
-			LOG_ERR("CMD_KEYSET length mismatch! %d/18", len);
 			break;
 		}
 		/**
@@ -342,7 +341,6 @@ static int pd_decode_command(struct osdp_pd *pd, uint8_t *buf, int len)
 			break;
 		}
 		if (len != CMD_CHLNG_DATA_LEN) {
-			LOG_ERR("CMD_CHLNG length mismatch! %d/8", len);
 			break;
 		}
 		osdp_sc_init(pd);
@@ -356,7 +354,6 @@ static int pd_decode_command(struct osdp_pd *pd, uint8_t *buf, int len)
 	}
 	case CMD_SCRYPT:
 		if (len != CMD_SCRYPT_DATA_LEN) {
-			LOG_ERR("CMD_SCRYPT length mismatch! %d/16", len);
 			break;
 		}
 		for (i = 0; i < 16; i++) {
@@ -373,11 +370,12 @@ static int pd_decode_command(struct osdp_pd *pd, uint8_t *buf, int len)
 		return OSDP_PD_ERR_REPLY;
 	}
 
-	if (ret != 0) {
-		LOG_ERR("Invalid command structure. CMD: %02x, Len: %d",
-			pd->cmd_id, len);
+	if (ret == OSDP_PD_ERR_GENERIC) {
+		LOG_ERR("Failed to decode command: CMD(%02x) Len:%d ret:%d",
+			pd->cmd_id, len, ret);
 		pd->reply_id = REPLY_NAK;
 		pd->cmd_data[0] = OSDP_PD_NAK_CMD_LEN;
+		ret = OSDP_PD_ERR_REPLY;
 	}
 
 	if (pd->cmd_id != CMD_POLL) {
@@ -387,6 +385,12 @@ static int pd_decode_command(struct osdp_pd *pd, uint8_t *buf, int len)
 	return ret;
 }
 
+static inline void assert_buf_len(int need, int have)
+{
+	__ASSERT(need < have, "OOM at build command: need:%d have:%d",
+		 need, have);
+}
+
 /**
  * Returns:
  * +ve: length of command
@@ -404,25 +408,15 @@ static int pd_build_reply(struct osdp_pd *pd, uint8_t *buf, int max_len)
 #endif
 	buf += data_off;
 	max_len -= data_off;
-	if (max_len <= 0) {
-		LOG_ERR("Out of buffer space!");
-		return -1;
-	}
 
 	switch (pd->reply_id) {
 	case REPLY_ACK:
-		if (max_len < REPLY_ACK_LEN) {
-			LOG_ERR("Out of buffer space!");
-			break;
-		}
+		assert_buf_len(REPLY_ACK_LEN, max_len);
 		buf[len++] = pd->reply_id;
 		ret = OSDP_PD_ERR_NONE;
 		break;
 	case REPLY_PDID:
-		if (max_len < REPLY_PDID_LEN) {
-			LOG_ERR("Out of buffer space!");
-			break;
-		}
+		assert_buf_len(REPLY_PDID_LEN, max_len);
 		buf[len++] = pd->reply_id;
 
 		buf[len++] = BYTE_0(pd->id.vendor_code);
@@ -443,10 +437,7 @@ static int pd_build_reply(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		ret = OSDP_PD_ERR_NONE;
 		break;
 	case REPLY_PDCAP:
-		if (max_len < REPLY_PDCAP_LEN) {
-			LOG_ERR("Out of buffer space!");
-			break;
-		}
+		assert_buf_len(REPLY_PDCAP_LEN, max_len);
 		buf[len++] = pd->reply_id;
 		for (i = 0; i < OSDP_PD_CAP_SENTINEL; i++) {
 			if (pd->cap[i].function_code != i) {
@@ -464,29 +455,20 @@ static int pd_build_reply(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		ret = OSDP_PD_ERR_NONE;
 		break;
 	case REPLY_LSTATR:
-		if (max_len < REPLY_LSTATR_LEN) {
-			LOG_ERR("Out of buffer space!");
-			break;
-		}
+		assert_buf_len(REPLY_LSTATR_LEN, max_len);
 		buf[len++] = pd->reply_id;
 		buf[len++] = ISSET_FLAG(pd, PD_FLAG_TAMPER);
 		buf[len++] = ISSET_FLAG(pd, PD_FLAG_POWER);
 		ret = OSDP_PD_ERR_NONE;
 		break;
 	case REPLY_RSTATR:
-		if (max_len < REPLY_RSTATR_LEN) {
-			LOG_ERR("Out of buffer space!");
-			break;
-		}
+		assert_buf_len(REPLY_RSTATR_LEN, max_len);
 		buf[len++] = pd->reply_id;
 		buf[len++] = ISSET_FLAG(pd, PD_FLAG_R_TAMPER);
 		ret = OSDP_PD_ERR_NONE;
 		break;
 	case REPLY_COM:
-		if (max_len < REPLY_COM_LEN) {
-			LOG_ERR("Out of buffer space!");
-			break;
-		}
+		assert_buf_len(REPLY_COM_LEN, max_len);
 		/**
 		 * If COMSET succeeds, the PD must reply with the old params and
 		 * then switch to the new params from then then on. We have the
@@ -517,10 +499,7 @@ static int pd_build_reply(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		ret = OSDP_PD_ERR_NONE;
 		break;
 	case REPLY_NAK:
-		if (max_len < REPLY_NAK_LEN) {
-			LOG_ERR("Fatal: insufficient space for sending NAK");
-			return -1;
-		}
+		assert_buf_len(REPLY_NAK_LEN, max_len);
 		buf[len++] = pd->reply_id;
 		buf[len++] = pd->cmd_data[0];
 		ret = OSDP_PD_ERR_NONE;
@@ -530,10 +509,7 @@ static int pd_build_reply(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		if (smb == NULL) {
 			break;
 		}
-		if (max_len < REPLY_CCRYPT_LEN) {
-			LOG_ERR("Out of buffer space!");
-			return -1;
-		}
+		assert_buf_len(REPLY_CCRYPT_LEN, max_len);
 		osdp_fill_random(pd->sc.pd_random, 8);
 		osdp_compute_session_keys(pd);
 		osdp_compute_pd_cryptogram(pd);
@@ -556,10 +532,7 @@ static int pd_build_reply(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		if (smb == NULL) {
 			break;
 		}
-		if (max_len < REPLY_RMAC_I_LEN) {
-			LOG_ERR("Out of buffer space!");
-			return -1;
-		}
+		assert_buf_len(REPLY_RMAC_I_LEN, max_len);
 		osdp_compute_rmac_i(pd);
 		buf[len++] = pd->reply_id;
 		for (i = 0; i < 16; i++) {
@@ -595,10 +568,7 @@ static int pd_build_reply(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		/* catch all errors and report it as a RECORD error to CP */
 		LOG_ERR("Failed to build REPLY(%02x); Sending NAK instead!",
 			pd->reply_id);
-		if (max_len < REPLY_NAK_LEN) {
-			LOG_ERR("Fatal: insufficient space for sending NAK");
-			return -1;
-		}
+		assert_buf_len(REPLY_NAK_LEN, max_len);
 		buf[0] = REPLY_NAK;
 		buf[1] = OSDP_PD_NAK_RECORD;
 		len = 2;