diff --git a/src/posix/platform/radio.cpp b/src/posix/platform/radio.cpp
index 0f21d64e2..721f71100 100644
--- a/src/posix/platform/radio.cpp
+++ b/src/posix/platform/radio.cpp
@@ -403,7 +403,7 @@ otError otPlatDiagProcess(otInstance *aInstance,
     char *cur                                              = cmd;
     char *end                                              = cmd + sizeof(cmd);
 
-    for (uint8_t index = 0; index < aArgsLength; index++)
+    for (uint8_t index = 0; (index < aArgsLength) && (cur < end); index++)
     {
         cur += snprintf(cur, static_cast<size_t>(end - cur), "%s ", aArgs[index]);
     }