From 8a3add3c6a7ad900e19d2ed7760627612aa3d17d Mon Sep 17 00:00:00 2001 From: Joshua Valluru <326636767+joshua-berri@users.noreply.github.com> Date: Tue, 15 Sep 2026 18:27:25 -0700 Subject: [PATCH] fix(mcp): reject scheme-only Basic credentials --- litellm/proxy/_experimental/mcp_server/upstream.py | 3 ++- .../mcp_server/test_mcp_server_manager.py | 13 ++++++++++++- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/litellm/proxy/_experimental/mcp_server/upstream.py b/litellm/proxy/_experimental/mcp_server/upstream.py index 8d7a7dba252..89fd1ad5066 100644 --- a/litellm/proxy/_experimental/mcp_server/upstream.py +++ b/litellm/proxy/_experimental/mcp_server/upstream.py @@ -29,7 +29,8 @@ def _usable_credential_value(auth_type: MCPAuthType, name: str, value: str) -> b if len(parts) != 2 or parts[0].lower() != "basic": return False try: - return bool(base64.b64decode(parts[1], validate=True).strip()) + decoded: Final = base64.b64decode(parts[1], validate=True).strip() + return bool(decoded) and decoded.lower() != b"basic" except ValueError: return False return True diff --git a/tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_server_manager.py b/tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_server_manager.py index ea05035e16f..e2275d05fcf 100644 --- a/tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_server_manager.py +++ b/tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_server_manager.py @@ -13638,10 +13638,21 @@ class TestProtectedCredentialPreparation: assert exc.value.status_code == 500 @pytest.mark.asyncio - @pytest.mark.parametrize("header", ["Basic", "Basic @@@", "Other abc"]) + @pytest.mark.parametrize("header", ["Basic", "Basic @@@", "Other abc", "Basic QmFzaWM="]) async def test_basic_headers_without_usable_credentials_reject(self, header: str) -> None: server = MCPServer(server_id="bad-basic", name="bad-basic", url="https://upstream.example/mcp", transport=MCPTransport.http, auth_type=MCPAuth.basic) with pytest.raises(HTTPException) as exc: await MCPServerManager()._create_mcp_client(server, extra_headers={"Authorization": header}) assert exc.value.status_code == 500 + + @pytest.mark.asyncio + @pytest.mark.parametrize("value", ["Basic", "Basic ", "basic"]) + @pytest.mark.parametrize("source", ["configured", "caller"]) + async def test_basic_scheme_alone_is_not_a_credential(self, value: str, source: str) -> None: + server = MCPServer(server_id="basic-scheme", name="basic-scheme", url="https://upstream.example/mcp", + transport=MCPTransport.http, auth_type=MCPAuth.basic, + authentication_token=value if source == "configured" else None) + with pytest.raises(HTTPException) as exc: + await MCPServerManager()._create_mcp_client(server, mcp_auth_header=value if source == "caller" else None) + assert exc.value.status_code == 500