diff --git a/src/lib_ccx/ccx_encoders_sami.c b/src/lib_ccx/ccx_encoders_sami.c
index 212f66504..23f458278 100644
--- a/src/lib_ccx/ccx_encoders_sami.c
+++ b/src/lib_ccx/ccx_encoders_sami.c
@@ -47,7 +47,7 @@ int write_stringz_as_sami(char *string, struct encoder_ctx *context, LLONG ms_st
 	// Scan for \n in the string and replace it with a 0
 	while (pos_r < len)
 	{
-		if (string[pos_r] == '\\' && string[pos_r + 1] == 'n')
+		if (pos_r < len - 1 && string[pos_r] == '\\' && string[pos_r + 1] == 'n')
 		{
 			unescaped[pos_w] = 0;
 			pos_r += 2;
@@ -62,7 +62,7 @@ int write_stringz_as_sami(char *string, struct encoder_ctx *context, LLONG ms_st
 	unescaped[pos_w] = 0;
 	// Now read the unescaped string (now several string'z and write them)
 	unsigned char *begin = unescaped;
-	while (begin < unescaped + len)
+	while (begin < unescaped + pos_w)
 	{
 		unsigned int u = encode_line(context, el, begin);
 		if (context->encoding != CCX_ENC_UNICODE)
diff --git a/src/lib_ccx/ccx_encoders_smptett.c b/src/lib_ccx/ccx_encoders_smptett.c
index 794f770ae..0919b392c 100644
--- a/src/lib_ccx/ccx_encoders_smptett.c
+++ b/src/lib_ccx/ccx_encoders_smptett.c
@@ -61,7 +61,7 @@ void write_stringz_as_smptett(char *string, struct encoder_ctx *context, LLONG m
 	// Scan for \n in the string and replace it with a 0
 	while (pos_r < len)
 	{
-		if (string[pos_r] == '\\' && string[pos_r + 1] == 'n')
+		if (pos_r < len - 1 && string[pos_r] == '\\' && string[pos_r + 1] == 'n')
 		{
 			unescaped[pos_w] = 0;
 			pos_r += 2;
@@ -76,7 +76,7 @@ void write_stringz_as_smptett(char *string, struct encoder_ctx *context, LLONG m
 	unescaped[pos_w] = 0;
 	// Now read the unescaped string (now several string'z and write them)
 	unsigned char *begin = unescaped;
-	while (begin < unescaped + len)
+	while (begin < unescaped + pos_w)
 	{
 		unsigned int u = encode_line(context, el, begin);
 		if (context->encoding != CCX_ENC_UNICODE)
diff --git a/src/lib_ccx/ccx_encoders_webvtt.c b/src/lib_ccx/ccx_encoders_webvtt.c
index fe03a541c..b1bce7293 100644
--- a/src/lib_ccx/ccx_encoders_webvtt.c
+++ b/src/lib_ccx/ccx_encoders_webvtt.c
@@ -155,7 +155,7 @@ int write_stringz_as_webvtt(char *string, struct encoder_ctx *context, LLONG ms_
 	// Scan for \n in the string and replace it with a 0
 	while (pos_r < len)
 	{
-		if (string[pos_r] == '\\' && string[pos_r + 1] == 'n')
+		if (pos_r < len - 1 && string[pos_r] == '\\' && string[pos_r + 1] == 'n')
 		{
 			unescaped[pos_w] = 0;
 			pos_r += 2;
@@ -170,7 +170,7 @@ int write_stringz_as_webvtt(char *string, struct encoder_ctx *context, LLONG ms_
 	unescaped[pos_w] = 0;
 	// Now read the unescaped string (now several string'z and write them)
 	unsigned char *begin = unescaped;
-	while (begin < unescaped + len)
+	while (begin < unescaped + pos_w)
 	{
 		unsigned int u = encode_line(context, el, begin);
 		if (context->encoding != CCX_ENC_UNICODE)