diff --git a/src/zm_fifo_debug.cpp b/src/zm_fifo_debug.cpp
index 1b1950e3c..0beaeb6b1 100644
--- a/src/zm_fifo_debug.cpp
+++ b/src/zm_fifo_debug.cpp
@@ -81,7 +81,11 @@ void zmFifoDbgOutput(
     int len = va_arg(arg_ptr, int);
     dbg_ptr += snprintf(dbg_ptr, str_size-(dbg_ptr-dbg_string), "%d:", len);
     for ( int i = 0; i < len; i++ ) {
-      dbg_ptr += snprintf(dbg_ptr, str_size-(dbg_ptr-dbg_string), " %02x", data[i]);
+      const auto max_len = str_size - (dbg_ptr - dbg_string);
+      int rc = snprintf(dbg_ptr, max_len, " %02x", data[i]);
+      if (rc < 0 || rc > max_len)
+        break;
+      dbg_ptr += rc;
     }
   } else {
     dbg_ptr += vsnprintf(dbg_ptr, str_size-(dbg_ptr-dbg_string), fstring, arg_ptr);
diff --git a/src/zm_logger.cpp b/src/zm_logger.cpp
index 4db535a78..87b2f692e 100644
--- a/src/zm_logger.cpp
+++ b/src/zm_logger.cpp
@@ -481,7 +481,11 @@ void Logger::logPrint(bool hex, const char *filepath, int line, int level, const
     int i;
     logPtr += snprintf(logPtr, sizeof(logString)-(logPtr-logString), "%d:", len);
     for ( i = 0; i < len; i++ ) {
-      logPtr += snprintf(logPtr, sizeof(logString)-(logPtr-logString), " %02x", data[i]);
+      const size_t max_len = sizeof(logString) - (logPtr - logString);
+      int rc = snprintf(logPtr, max_len, " %02x", data[i]);
+      if (rc < 0 || static_cast<size_t>(rc) > max_len)
+        break;
+      logPtr += rc;
     }
   } else {
     logPtr += vsnprintf(logPtr, sizeof(logString)-(logPtr-logString), fstring, argPtr);
diff --git a/src/zm_monitor.cpp b/src/zm_monitor.cpp
index b7828426b..ddfb6c19f 100644
--- a/src/zm_monitor.cpp
+++ b/src/zm_monitor.cpp
@@ -2742,24 +2742,29 @@ void Monitor::TimestampImage(Image *ts_image, SystemTimePoint ts_time) const {
 
   while (*s_ptr && ((unsigned int)(d_ptr - label_text) < (unsigned int) sizeof(label_text))) {
     if ( *s_ptr == config.timestamp_code_char[0] ) {
+      const auto max_len = sizeof(label_text) - (d_ptr - label_text);
       bool found_macro = false;
+      int rc = 0;
       switch ( *(s_ptr+1) ) {
         case 'N' :
-          d_ptr += snprintf(d_ptr, sizeof(label_text)-(d_ptr-label_text), "%s", name.c_str());
+          rc = snprintf(d_ptr, max_len, "%s", name.c_str());
           found_macro = true;
           break;
         case 'Q' :
-          d_ptr += snprintf(d_ptr, sizeof(label_text)-(d_ptr-label_text), "%s", trigger_data->trigger_showtext);
+          rc = snprintf(d_ptr, max_len, "%s", trigger_data->trigger_showtext);
           found_macro = true;
           break;
         case 'f' :
           typedef std::chrono::duration<int64, std::centi> Centiseconds;
           Centiseconds centi_sec = std::chrono::duration_cast<Centiseconds>(
               ts_time.time_since_epoch() - std::chrono::duration_cast<Seconds>(ts_time.time_since_epoch()));
-          d_ptr += snprintf(d_ptr, sizeof(label_text) - (d_ptr - label_text), "%02lld", static_cast<long long int>(centi_sec.count()));
+          rc = snprintf(d_ptr, max_len, "%02lld", static_cast<long long int>(centi_sec.count()));
           found_macro = true;
           break;
       }
+      if (rc < 0 || static_cast<size_t>(rc) > max_len)
+        break;
+      d_ptr += rc;
       if ( found_macro ) {
         s_ptr += 2;
         continue;