diff --git a/‎git/cmd.py‎
Lines changed: 6 additions & 4 deletions b/‎git/cmd.py‎
Lines changed: 6 additions & 4 deletions
diff --git a/‎test/test_command_guards.py‎
Lines changed: 23 additions & 0 deletions b/‎test/test_command_guards.py‎
Lines changed: 23 additions & 0 deletions
@@ -646,7 +646,8 @@ class Git(metaclass=_GitMeta):
     )
 
     # Match Git's leading transport selector, including an empty helper name.
-    re_unsafe_protocol = re.compile(r"([A-Za-z0-9][A-Za-z0-9+.-]*|)::")
+    # Git also selects the command-executing ext helper for an ext:// URL.
+    re_unsafe_protocol = re.compile(r"([A-Za-z0-9][A-Za-z0-9+.-]*|)::|ext://")
 
     unsafe_git_ls_remote_options = [
         # This option allows arbitrary command execution in git-ls-remote.
@@ -946,7 +947,8 @@ def check_unsafe_protocols(cls, url: str) -> None:
 
         Apart from the usual protocols (http, git, ssh), Git allows "remote helpers"
         that have the form ``<transport>::<address>``. One of these helpers (``ext::``)
-        can be used to invoke any arbitrary command.
+        can be used to invoke any arbitrary command. Git also selects that helper
+        for ``ext://`` URLs and interprets the URL as a command path.
 
         See:
 
@@ -955,9 +957,9 @@ def check_unsafe_protocols(cls, url: str) -> None:
         """
         match = cls.re_unsafe_protocol.match(url)
         if match:
-            protocol = match.group(1)
+            protocol = match.group(0)
             raise UnsafeProtocolError(
-                f"The `{protocol}::` protocol looks suspicious, use `allow_unsafe_protocols=True` to allow it."
+                f"The `{protocol}` protocol looks suspicious, use `allow_unsafe_protocols=True` to allow it."
             )
 
     @classmethod
 
@@ -36,6 +36,29 @@ def test_ls_remote_rejects_unsafe_protocols(args, kwargs, allow_unsafe_options):
         run.assert_not_called()
 
 
+@pytest.mark.parametrize("through_repo", (False, True))
+@pytest.mark.parametrize("remote", ("ext::helper", "ext://helper"))
+def test_ls_remote_protocol_guard_at_both_entry_points(tmp_path, through_repo, remote):
+    with Repo.init(tmp_path) as repo:
+        command = repo.git if through_repo else Git()
+        with mock.patch.object(Git, "execute", return_value="refs") as execute:
+            for allow_unsafe_options in (False, True):
+                with pytest.raises(UnsafeProtocolError):
+                    command.ls_remote(remote, allow_unsafe_options=allow_unsafe_options)
+            execute.assert_not_called()
+
+            url = "ssh://git@[2001:db8::1]/repo.git"
+            assert command.ls_remote(url) == "refs"
+            execute.assert_called_once_with([Git.GIT_PYTHON_GIT_EXECUTABLE, "ls-remote", url])
+            execute.reset_mock()
+
+            with pytest.raises(UnsafeOptionError):
+                command.ls_remote(remote, upload_pack="helper", allow_unsafe_protocols=True)
+            execute.assert_not_called()
+            assert command.ls_remote(remote, allow_unsafe_protocols=True) == "refs"
+            execute.assert_called_once_with([Git.GIT_PYTHON_GIT_EXECUTABLE, "ls-remote", remote])
+
+
 @pytest.mark.parametrize(
     "args, kwargs",
     [