diff --git a/client/src/cmdanalyse.c b/client/src/cmdanalyse.c
index e7c7c2334..d3456950d 100644
--- a/client/src/cmdanalyse.c
+++ b/client/src/cmdanalyse.c
@@ -1025,8 +1025,8 @@ static int CmdAnalyseFoo(const char *Cmd) {
     uint8_t data[256];
     CLIGetHexWithReturn(ctx, 1, data, &datalen);
 
-    int data3len = 512;
-    uint8_t data3[512];
+    uint8_t data3[512] = {0};
+    int data3len = sizeof(data3) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated;
     CLIGetStrWithReturn(ctx, 1, data3, &data3len);
 
     CLIParserFree(ctx);
diff --git a/client/src/cmddata.c b/client/src/cmddata.c
index 2a5b2474a..167d80b90 100644
--- a/client/src/cmddata.c
+++ b/client/src/cmddata.c
@@ -3386,8 +3386,8 @@ static int CmdAtrLookup(const char *Cmd) {
         arg_param_end
     };
     CLIExecWithReturn(ctx, Cmd, argtable, false);
-    int dlen = 128;
     uint8_t data[128 + 1];
+    int dlen = sizeof(data) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 1, data, &dlen);
 
 //    bool selftest = arg_get_lit(ctx, 2);
@@ -3574,12 +3574,12 @@ static int CmdBinaryMap(const char *Cmd) {
     };
     CLIExecWithReturn(ctx, Cmd, argtable, false);
 
-    int hlen = 5;
     uint8_t hex[5 + 1];
+    int hlen = sizeof(hex) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 1, hex, &hlen);
 
-    int tlen = 40;
     uint8_t template[40 + 1];
+    int tlen = sizeof(template) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 2, template, &tlen);
     CLIParserFree(ctx);
 
diff --git a/client/src/cmdhficlass.c b/client/src/cmdhficlass.c
index f70aebd31..fb31da17a 100644
--- a/client/src/cmdhficlass.c
+++ b/client/src/cmdhficlass.c
@@ -4599,8 +4599,9 @@ static int CmdHFiClassEncode(const char *Cmd) {
     };
     CLIExecWithReturn(ctx, Cmd, argtable, false);
 
-    int bin_len = 63;
+    // TODO: very confusing sizes... buf of 70, parser len to 63 instead of 70-1, tests for len > 127, loop with 64...
     uint8_t bin[70] = {0};
+    int bin_len = 63;
     CLIGetStrWithReturn(ctx, 1, bin, &bin_len);
 
     int key_nr = arg_get_int_def(ctx, 2, -1);
diff --git a/client/src/cmdhfjooki.c b/client/src/cmdhfjooki.c
index 3770974ca..3b7d9b63e 100644
--- a/client/src/cmdhfjooki.c
+++ b/client/src/cmdhfjooki.c
@@ -442,8 +442,8 @@ static int CmdHF14AJookiDecode(const char *Cmd) {
         arg_param_end
     };
     CLIExecWithReturn(ctx, Cmd, argtable, false);
-    int dlen = 16;
     uint8_t b64[JOOKI_B64_LEN] = {0x00};
+    int dlen = sizeof(b64) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     memset(b64, 0x0, sizeof(b64));
     CLIGetStrWithReturn(ctx, 1, b64, &dlen);
     bool verbose = arg_get_lit(ctx, 2);
@@ -471,8 +471,8 @@ static int CmdHF14AJookiSim(const char *Cmd) {
         arg_param_end
     };
     CLIExecWithReturn(ctx, Cmd, argtable, true);
-    int dlen = 16;
     uint8_t b64[JOOKI_B64_LEN] = {0x00};
+    int dlen = sizeof(b64) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     memset(b64, 0x0, sizeof(b64));
     CLIGetStrWithReturn(ctx, 1, b64, &dlen);
     CLIParserFree(ctx);
@@ -611,8 +611,8 @@ static int CmdHF14AJookiClone(const char *Cmd) {
         arg_param_end
     };
     CLIExecWithReturn(ctx, Cmd, argtable, false);
-    int blen = 16;
     uint8_t b64[JOOKI_B64_LEN] = {0x00};
+    int blen = sizeof(b64) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     memset(b64, 0x0, sizeof(b64));
     CLIGetStrWithReturn(ctx, 1, b64, &blen);
 
diff --git a/client/src/cmdhfmf.c b/client/src/cmdhfmf.c
index b6ecd40e4..cf65b6bcb 100644
--- a/client/src/cmdhfmf.c
+++ b/client/src/cmdhfmf.c
@@ -9257,8 +9257,8 @@ static int CmdHFMFHidEncode(const char *Cmd) {
     };
     CLIExecWithReturn(ctx, Cmd, argtable, false);
 
-    int bin_len = 120;
     uint8_t bin[121] = {0};
+    int bin_len = sizeof(bin) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 1, bin, &bin_len);
 
     wiegand_card_t card;
diff --git a/client/src/cmdhw.c b/client/src/cmdhw.c
index 7f6ba4b97..a270d2f1b 100644
--- a/client/src/cmdhw.c
+++ b/client/src/cmdhw.c
@@ -1358,8 +1358,8 @@ static int CmdConnect(const char *Cmd) {
     };
     CLIExecWithReturn(ctx, Cmd, argtable, true);
 
-    int p_len = FILE_PATH_SIZE;
     char port[FILE_PATH_SIZE] = {0};
+    int p_len = sizeof(port) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated;
     CLIGetStrWithReturn(ctx, 1, (uint8_t *)port, &p_len);
     uint32_t baudrate = arg_get_u32_def(ctx, 2, USART_BAUD_RATE);
     CLIParserFree(ctx);
diff --git a/client/src/cmdlf.c b/client/src/cmdlf.c
index 2a01f9c8c..58472cd0a 100644
--- a/client/src/cmdlf.c
+++ b/client/src/cmdlf.c
@@ -272,12 +272,12 @@ int CmdLFCommandRead(const char *Cmd) {
     CLIExecWithReturn(ctx, Cmd, argtable, false);
     uint32_t delay = arg_get_u32_def(ctx, 1, 0);
 
-    int cmd_len = 128;
     char cmd[128] = {0};
+    int cmd_len = sizeof(cmd) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 2, (uint8_t *)cmd, &cmd_len);
 
-    int extra_arg_len = 250;
     char extra_arg[250] = {0};
+    int extra_arg_len = sizeof(extra_arg) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 3, (uint8_t *)extra_arg, &extra_arg_len);
 
     uint16_t period_1 = arg_get_u32_def(ctx, 4, 0);
diff --git a/client/src/cmdlfem4x50.c b/client/src/cmdlfem4x50.c
index 9993243f4..aa128b53a 100644
--- a/client/src/cmdlfem4x50.c
+++ b/client/src/cmdlfem4x50.c
@@ -377,8 +377,8 @@ static int CmdEM4x50Brute(const char *Cmd) {
     em4x50_data_t etd;
     memset(&etd, 0, sizeof(etd));
 
-    int mode_len = 64;
     char mode[64];
+    int mode_len = sizeof(mode) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 1, (uint8_t *) mode, &mode_len);
     PrintAndLogEx(INFO, "Chosen mode: %s", mode);
 
diff --git a/client/src/cmdlfhid.c b/client/src/cmdlfhid.c
index e1cc1f00f..ab41f3798 100644
--- a/client/src/cmdlfhid.c
+++ b/client/src/cmdlfhid.c
@@ -375,6 +375,7 @@ static int CmdHIDClone(const char *Cmd) {
     bool q5 = arg_get_lit(ctx, 7);
     bool em = arg_get_lit(ctx, 8);
 
+    // TODO: very confusing sizes... buf of 70, parser len to 63 instead of 70-1, tests for len > 127, loop with 96...
     int bin_len = 63;
     uint8_t bin[70] = {0};
     CLIGetStrWithReturn(ctx, 9, bin, &bin_len);
diff --git a/client/src/cmdlfkeri.c b/client/src/cmdlfkeri.c
index b21a2deb4..1a390fa45 100644
--- a/client/src/cmdlfkeri.c
+++ b/client/src/cmdlfkeri.c
@@ -244,8 +244,8 @@ static int CmdKeriClone(const char *Cmd) {
     };
     CLIExecWithReturn(ctx, Cmd, argtable, false);
 
-    uint8_t keritype[2] = {'i'}; // default to internalid
-    int typeLen = sizeof(keritype);
+    uint8_t keritype[2] = {'i', 0}; // default to internalid
+    int typeLen = sizeof(keritype) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 1, keritype, &typeLen);
 
     uint32_t fc = arg_get_int_def(ctx, 2, 0);
diff --git a/client/src/cmdlfpac.c b/client/src/cmdlfpac.c
index 86ffebd4c..c1f6247f7 100644
--- a/client/src/cmdlfpac.c
+++ b/client/src/cmdlfpac.c
@@ -236,8 +236,8 @@ static int CmdPacClone(const char *Cmd) {
     };
     CLIExecWithReturn(ctx, Cmd, argtable, false);
 
-    uint8_t cnstr[9];
-    int cnlen = 9;
+    uint8_t cnstr[9] = {0};
+    int cnlen = sizeof(cnstr) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     memset(cnstr, 0x00, sizeof(cnstr));
     CLIGetStrWithReturn(ctx, 1, cnstr, &cnlen);
 
@@ -329,7 +329,7 @@ static int CmdPacSim(const char *Cmd) {
     CLIExecWithReturn(ctx, Cmd, argtable, false);
 
     uint8_t cnstr[10];
-    int cnlen = 9;
+    int cnlen = sizeof(cnstr) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     memset(cnstr, 0x00, sizeof(cnstr));
     CLIGetStrWithReturn(ctx, 1, cnstr, &cnlen);
 
diff --git a/client/src/cmdlfpresco.c b/client/src/cmdlfpresco.c
index bc816a79f..2fd78c724 100644
--- a/client/src/cmdlfpresco.c
+++ b/client/src/cmdlfpresco.c
@@ -189,8 +189,8 @@ static int CmdPrescoClone(const char *Cmd) {
     uint8_t hex[4] = {0, 0, 0, 0};
     CLIGetHexWithReturn(ctx, 1, hex, &hex_len);
 
-    uint8_t idstr[11];
-    int slen = 9;
+    uint8_t idstr[10];
+    int slen = sizeof(idstr) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     memset(idstr, 0x00, sizeof(idstr));
     CLIGetStrWithReturn(ctx, 2, idstr, &slen);
 
@@ -292,8 +292,8 @@ static int CmdPrescoSim(const char *Cmd) {
     uint8_t hex[4] = {0, 0, 0, 0};
     CLIGetHexWithReturn(ctx, 1, hex, &hex_len);
 
-    uint8_t idstr[11];
-    int slen = 9;
+    uint8_t idstr[10] = {0};
+    int slen = sizeof(idstr) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     memset(idstr, 0x00, sizeof(idstr));
     CLIGetStrWithReturn(ctx, 2, idstr, &slen);
     CLIParserFree(ctx);
diff --git a/client/src/cmdlft55xx.c b/client/src/cmdlft55xx.c
index 38a65ea72..d0da08d99 100644
--- a/client/src/cmdlft55xx.c
+++ b/client/src/cmdlft55xx.c
@@ -1952,8 +1952,8 @@ static int CmdT55xxDangerousRaw(const char *Cmd) {
     ng.bitlen = 0;
     memset(ng.data, 0x00, sizeof(ng.data));
 
-    int bin_len = 127;
     uint8_t bin[128] = {0};
+    int bin_len = sizeof(bin) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 1, bin, &bin_len);
 
     ng.time = arg_get_int_def(ctx, 2, 0);
diff --git a/client/src/cmdsmartcard.c b/client/src/cmdsmartcard.c
index da81c8249..a6a07c4c6 100644
--- a/client/src/cmdsmartcard.c
+++ b/client/src/cmdsmartcard.c
@@ -1253,14 +1253,14 @@ static int CmdPCSC(const char *Cmd) {
     CLIExecWithReturn(ctx, Cmd, argtable, true);
 
     uint8_t host[100] = {0};
-    int hostLen = sizeof(host);
+    int hostLen = sizeof(host) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 1, host, &hostLen);
     if (hostLen == 0) {
         strcpy((char *) host, "localhost");
     }
 
     uint8_t port[6] = {0};
-    int portLen = sizeof(port);
+    int portLen = sizeof(port) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 2, port, &portLen);
     if (portLen == 0) {
         strcpy((char *) port, "35963");
diff --git a/client/src/emv/cmdemv.c b/client/src/emv/cmdemv.c
index bb00d7431..32d73ccb1 100644
--- a/client/src/emv/cmdemv.c
+++ b/client/src/emv/cmdemv.c
@@ -2041,7 +2041,7 @@ static int CmdEMVScan(const char *Cmd) {
     uint8_t psenum = (channel == CC_CONTACT) ? 1 : 2;
 
     uint8_t filename[FILE_PATH_SIZE] = {0};
-    int filenamelen = sizeof(filename);
+    int filenamelen = sizeof(filename) - 1; // CLIGetStrWithReturn does not guarantee string to be null-terminated
     CLIGetStrWithReturn(ctx, 12, filename, &filenamelen);
 
     CLIParserFree(ctx);
diff --git a/doc/cliparser.md b/doc/cliparser.md
index 118a82c86..33af8df55 100644
--- a/doc/cliparser.md
+++ b/doc/cliparser.md
@@ -256,8 +256,8 @@ CLIGetHexWithReturn(\<context\>, \<opt index\>, \<store variable\>, \<ptr to sto
 CLIGetStrWithReturn(\<context\>,\<opt index\>, \<uint8_t \*\>, \<int \*\>);
     If failed to retrieve string, it will exit fct
 
-    uint8_t buffer[100];
-    int slen = sizeof(buffer); // <- slen MUST be the maximum number of characters that you want returned. e.g. Buffer Size
+    uint8_t buffer[100] = {0};
+    int slen = sizeof(buffer) - 1; // <- slen MUST be the maximum number of characters that you want returned. e.g. Buffer Size - 1 if you need it to be null-terminated!
     CLIGetStrWithReturn(ctx, 1, buffer, &slen);
 
 **string option**