@@ -57,9 +57,24 @@ def _call_plugin(self, cmd: str, input_json: str) -> str:
         request = length_bytes_le + input_json.encode()
 
         # Call plugin
-        process_result = subprocess.run(
-            [cmd], input=request, capture_output=True, check=True
-        )
+        process_result = subprocess.run([cmd], input=request, capture_output=True)
+
+        if process_result.returncode != 0:
+            stdout_bytes = process_result.stdout
+            if (
+                len(stdout_bytes) >= 4
+                and struct.unpack("<I", stdout_bytes[:4])[0] == len(stdout_bytes) - 4
+            ):
+                stdout_bytes = stdout_bytes[4:]
+
+            error_msg = "Command '{}' returned non-zero exit status {}.\nStdout: {}\nStderr: {}".format(
+                cmd,
+                process_result.returncode,
+                stdout_bytes.decode(errors="replace").strip(),
+                process_result.stderr.decode(errors="replace").strip(),
+            )
+
+            raise exceptions.GoogleAuthError(error_msg)
 
         # Check length of response
         response_len_le = process_result.stdout[:4]
 
@@ -49,6 +49,7 @@ def test_malformated_get_assertion_response(os_get_stub, subprocess_run_stub):
     response_len = struct.pack("<I", 5)
     response = "1234567890"
     mock_response = mock.Mock()
+    mock_response.returncode = 0
     mock_response.stdout = response_len + response.encode()
     subprocess_run_stub.return_value = mock_response
 
@@ -68,6 +69,7 @@ def test_failure_get_assertion(os_get_stub, subprocess_run_stub):
 
     # process returns get response in json
     mock_response = mock.Mock()
+    mock_response.returncode = 0
     mock_response.stdout = response_len + response_json
     subprocess_run_stub.return_value = mock_response
 
@@ -96,6 +98,7 @@ def test_success_get_assertion(os_get_stub, subprocess_run_stub):
 
     # process returns get response in json
     mock_response = mock.Mock()
+    mock_response.returncode = 0
     mock_response.stdout = valid_plugin_response_len + valid_plugin_response_json
     subprocess_run_stub.return_value = mock_response
 
@@ -146,3 +149,21 @@ def test_success_get_assertion(os_get_stub, subprocess_run_stub):
     assert (
         got_response.response.user_handle == success_response["response"]["userHandle"]
     )
+
+
+def test_plugin_nonzero_exit(os_get_stub, subprocess_run_stub):
+    response_json = b"detailed_gnubby_internal_crash_log"
+    response_len = struct.pack("<I", len(response_json))
+
+    mock_response = mock.Mock()
+    mock_response.returncode = 1
+    mock_response.stdout = response_len + response_json
+    mock_response.stderr = b"stderr dump"
+    subprocess_run_stub.return_value = mock_response
+
+    test_handler = webauthn_handler.PluginHandler()
+    with pytest.raises(exceptions.GoogleAuthError) as excinfo:
+        test_handler.get(GET_ASSERTION_REQUEST)
+
+    assert "returned non-zero exit status 1" in str(excinfo.value)
+    assert "detailed_gnubby_internal_crash_log" in str(excinfo.value)