diff --git a/test_testping1.py b/test_testping1.py
index a3fcd04..622fbbd 100644
--- a/test_testping1.py
+++ b/test_testping1.py
@@ -246,6 +246,19 @@ def test_is_reachable_ipv6_scope_id_validation(self, mock_call):
             self.assertIn("Invalid IPv6 scope ID: IPv6Address('fe80::1%eth0\\nERROR:root:Compromised')", log.output[0])
             mock_call.assert_not_called()
 
+    @patch('testping1.subprocess.call')
+    def test_is_reachable_ipv6_scope_id_length_limit(self, mock_call):
+        """Test is_reachable enforces strict length limit on IPv6 scope IDs."""
+        import ipaddress
+        # Max Linux IFNAMSIZ is 15. Provide 16 chars.
+        malicious_ip_obj = ipaddress.IPv6Address('fe80::1')
+        malicious_ip_obj._scope_id = 'a' * 16
+
+        with self.assertLogs(level='ERROR') as log:
+            self.assertFalse(is_reachable(malicious_ip_obj))
+            self.assertIn("Invalid IPv6 scope ID:", log.output[0])
+            mock_call.assert_not_called()
+
     @patch('testping1.subprocess.call')
     def test_is_reachable_subprocess_timeout(self, mock_call):
         """Test is_reachable handles subprocess.TimeoutExpired securely."""
diff --git a/testping1.py b/testping1.py
index 63e23a5..9393a6b 100644
--- a/testping1.py
+++ b/testping1.py
@@ -15,7 +15,9 @@
 # Calling re.compile() once at module load avoids the overhead of parsing and compiling
 # the regular expression (or looking it up in the internal cache) during every is_reachable() execution.
 # This yields a measurable CPU speedup when firing thousands of concurrent pings.
-SCOPE_ID_REGEX = re.compile(r'[\w\-]+')
+# 🛡️ Sentinel: Enforce strict length limits (1-15 chars) and explicit ASCII charset
+# to prevent resource exhaustion or unexpected OS behavior from overly long/Unicode scope IDs.
+SCOPE_ID_REGEX = re.compile(r'[a-zA-Z0-9_\-]{1,15}')
 
 # ⚡ Bolt: Cache the absolute path of the ping executable.
 # Calling shutil.which() once at module load avoids the overhead of traversing