CVE-2026-49257

mcp-pinot is a Python-based Model Context Protocol (MCP) server for interacting with Apache Pinot. In versions 3.0.1 and below, mcp-pinot defaults to running an HTTP MCP server bound to 0.0.0.0:8080 with no authentication enabled. All MCP tools, including SQL query execution, schema creation, and table-config mutation, are reachable by any network-adjacent caller. The server proxies these calls using server-side Pinot credentials, producing a confused-deputy condition that yields full read/write access to the configured Pinot cluster. This issue has been fixed in version 3.1.0

mcp-pinot is a Python-based Model Context Protocol (MCP) server for interacting with Apache Pinot. In versions 3.0.1 and below, mcp-pinot defaults to running an HTTP MCP server bound to 0.0.0.0:8080 with no authentication enabled. All MCP tools, including SQL query execution, schema creation, and table-config mutation, are reachable by any network-adjacent caller. The server proxies these calls using server-side Pinot credentials, producing a confused-deputy condition that yields full read/write access to the configured Pinot cluster. This issue has been fixed in version 3.1.0

Resolution

Fixed in v3.1.0, released 2026-05-25. The fix was merged in PR #95 at commit 1c7d3f9.

The fix changes the default HTTP bind host to 127.0.0.1, refuses non-loopback HTTP/HTTPS exposure unless OAuth is enabled, makes Helm exposure opt-in and OAuth-gated, and adds parser-backed single-statement read-only validation for read-query.

CVSS evaluation

Reviewed on 2026-05-25. The advisory remains Critical with CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H = 10.0.

Rationale:

| Metric | Value | Reason | |---|---|---| | AV | Network | The default HTTP server bound to 0.0.0.0:8080 and accepted remote HTTP requests. | | AC | Low | Exploitation required only a direct MCP tool call. | | PR | None | OAuth was disabled by default. | | UI | None | No user interaction was required. | | S | Changed | The vulnerable MCP server used its server-side credentials to act on the separate Pinot cluster security boundary. | | C | High | Unauthenticated callers could read table data and cluster metadata through server-side Pinot credentials. | | I | High | Unauthenticated callers could create or update schemas and table configs where the server-side account had those privileges. | | A | High | Expensive queries and configuration mutations could degrade or disrupt Pinot availability. |

Unauthenticated tool invocation via default oauth_enabled=False + host 0.0.0.0 bind

Summary

mcp-pinot v3.0.1 (and earlier) defaults to running an HTTP MCP server bound to 0.0.0.0:8080 with no authentication enabled. All MCP tools, including SQL query execution, schema creation, and table-config mutation, are reachable by any network-adjacent caller. The server proxies these calls using server-side Pinot credentials, producing a confused-deputy condition that yields full read/write access to the configured Pinot cluster.

Affected versions

• All releases on main, confirmed in tags v2.1.0 through v3.0.1.
• Affected files: mcp_pinot/server.py, mcp_pinot/config.py.

Root cause

Three defaults compose to produce unauthenticated network exposure:

1. Auth is opt-in and defaults to off (mcp_pinot/config.py:64,328):

@dataclass
class ServerConfig:
    ...
    oauth_enabled: bool = False
    ...

def load_server_config() -> ServerConfig:
    return ServerConfig(
        ...
        oauth_enabled=os.getenv("OAUTH_ENABLED", "false").lower() == "true",
        ...
    )

2. Auth construction is gated by oauth_enabled (mcp_pinot/server.py:26-46):

_auth = None
if server_config.oauth_enabled:
    oauth_config = load_oauth_config()
    token_verifier = JWTVerifier(...)
    _auth = OAuthProxy(...)

mcp = FastMCP("Pinot MCP Server", auth=_auth)

When oauth_enabled is false (default), _auth stays None and FastMCP registers all @mcp.tool endpoints with no authentication.

3. Default bind is all interfaces on a well-known port (mcp_pinot/config.py:60-61):

host: str = "0.0.0.0"
port: int = 8080

The HTTP transport in server.py:263-268 uses these values directly. Any operator following the README's HTTP transport instructions (uv pip install, .env from .env.example, run) ends up with a network-reachable MCP server with no auth.

Confused-deputy

The Pinot client uses server-side credentials loaded from environment variables (mcp_pinot/config.py:285-294, 300-315). When an unauthenticated MCP caller invokes read_query or any other tool, the request is executed with the server's PINOT_TOKEN or PINOT_USERNAME/PINOT_PASSWORD, which is typically a privileged service account. The MCP server effectively launders the caller's lack of identity into the server's privileges against the upstream cluster.

Exposed tools

All 14 tools in…

mcp-pinot is a Python-based Model Context Protocol (MCP) server for interacting with Apache Pinot. In versions 3.0.1 and below, mcp-pinot defaults to running an HTTP MCP server bound to 0.0.0.0:8080 with no authentication enabled. All MCP tools, including SQL query execution, schema creation, and table-config mutation, are reachable by any network-adjacent caller. The server proxies these calls using server-side Pinot credentials, producing a confused-deputy condition that yields full read/write access to the configured Pinot cluster. This issue has been fixed in version 3.1.0

mcp-pinot is a Python-based Model Context Protocol (MCP) server for interacting with Apache Pinot. In versions 3.0.1 and below, mcp-pinot defaults to running an HTTP MCP server bound to 0.0.0.0:8080 with no authentication enabled. All MCP tools, including SQL query execution, schema creation, and table-config mutation, are reachable by any network-adjacent caller. The server proxies these calls using server-side Pinot credentials, producing a confused-deputy condition that yields full read/write access to the configured Pinot cluster. This issue has been fixed in version 3.1.0

Resolution

Fixed in v3.1.0, released 2026-05-25. The fix was merged in PR #95 at commit 1c7d3f9.

The fix changes the default HTTP bind host to 127.0.0.1, refuses non-loopback HTTP/HTTPS exposure unless OAuth is enabled, makes Helm exposure opt-in and OAuth-gated, and adds parser-backed single-statement read-only validation for read-query.

CVSS evaluation

Reviewed on 2026-05-25. The advisory remains Critical with CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H = 10.0.

Rationale:

| Metric | Value | Reason | |---|---|---| | AV | Network | The default HTTP server bound to 0.0.0.0:8080 and accepted remote HTTP requests. | | AC | Low | Exploitation required only a direct MCP tool call. | | PR | None | OAuth was disabled by default. | | UI | None | No user interaction was required. | | S | Changed | The vulnerable MCP server used its server-side credentials to act on the separate Pinot cluster security boundary. | | C | High | Unauthenticated callers could read table data and cluster metadata through server-side Pinot credentials. | | I | High | Unauthenticated callers could create or update schemas and table configs where the server-side account had those privileges. | | A | High | Expensive queries and configuration mutations could degrade or disrupt Pinot availability. |

Unauthenticated tool invocation via default oauth_enabled=False + host 0.0.0.0 bind

Summary

mcp-pinot v3.0.1 (and earlier) defaults to running an HTTP MCP server bound to 0.0.0.0:8080 with no authentication enabled. All MCP tools, including SQL query execution, schema creation, and table-config mutation, are reachable by any network-adjacent caller. The server proxies these calls using server-side Pinot credentials, producing a confused-deputy condition that yields full read/write access to the configured Pinot cluster.

Affected versions

• All releases on main, confirmed in tags v2.1.0 through v3.0.1.
• Affected files: mcp_pinot/server.py, mcp_pinot/config.py.

Root cause

Three defaults compose to produce unauthenticated network exposure:

1. Auth is opt-in and defaults to off (mcp_pinot/config.py:64,328):

@dataclass
class ServerConfig:
    ...
    oauth_enabled: bool = False
    ...

def load_server_config() -> ServerConfig:
    return ServerConfig(
        ...
        oauth_enabled=os.getenv("OAUTH_ENABLED", "false").lower() == "true",
        ...
    )

2. Auth construction is gated by oauth_enabled (mcp_pinot/server.py:26-46):

_auth = None
if server_config.oauth_enabled:
    oauth_config = load_oauth_config()
    token_verifier = JWTVerifier(...)
    _auth = OAuthProxy(...)

mcp = FastMCP("Pinot MCP Server", auth=_auth)

When oauth_enabled is false (default), _auth stays None and FastMCP registers all @mcp.tool endpoints with no authentication.

3. Default bind is all interfaces on a well-known port (mcp_pinot/config.py:60-61):

host: str = "0.0.0.0"
port: int = 8080

The HTTP transport in server.py:263-268 uses these values directly. Any operator following the README's HTTP transport instructions (uv pip install, .env from .env.example, run) ends up with a network-reachable MCP server with no auth.

Confused-deputy

The Pinot client uses server-side credentials loaded from environment variables (mcp_pinot/config.py:285-294, 300-315). When an unauthenticated MCP caller invokes read_query or any other tool, the request is executed with the server's PINOT_TOKEN or PINOT_USERNAME/PINOT_PASSWORD, which is typically a privileged service account. The MCP server effectively launders the caller's lack of identity into the server's privileges against the upstream cluster.

Exposed tools

All 14 tools in…

Resolution

Fixed in v3.1.0, released 2026-05-25. The fix was merged in PR #95 at commit 1c7d3f9.

The fix changes the default HTTP bind host to 127.0.0.1, refuses non-loopback HTTP/HTTPS exposure unless OAuth is enabled, makes Helm exposure opt-in and OAuth-gated, and adds parser-backed single-statement read-only validation for read-query.

CVSS evaluation

Reviewed on 2026-05-25. The advisory remains Critical with CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H = 10.0.

Rationale:

| Metric | Value | Reason | |---|---|---| | AV | Network | The default HTTP server bound to 0.0.0.0:8080 and accepted remote HTTP requests. | | AC | Low | Exploitation required only a direct MCP tool call. | | PR | None | OAuth was disabled by default. | | UI | None | No user interaction was required. | | S | Changed | The vulnerable MCP server used its server-side credentials to act on the separate Pinot cluster security boundary. | | C | High | Unauthenticated callers could read table data and cluster metadata through server-side Pinot credentials. | | I | High | Unauthenticated callers could create or update schemas and table configs where the server-side account had those privileges. | | A | High | Expensive queries and configuration mutations could degrade or disrupt Pinot availability. |

Unauthenticated tool invocation via default oauth_enabled=False + host 0.0.0.0 bind

Summary

mcp-pinot v3.0.1 (and earlier) defaults to running an HTTP MCP server bound to 0.0.0.0:8080 with no authentication enabled. All MCP tools, including SQL query execution, schema creation, and table-config mutation, are reachable by any network-adjacent caller. The server proxies these calls using server-side Pinot credentials, producing a confused-deputy condition that yields full read/write access to the configured Pinot cluster.

Affected versions

• All releases on main, confirmed in tags v2.1.0 through v3.0.1.
• Affected files: mcp_pinot/server.py, mcp_pinot/config.py.

Root cause

Three defaults compose to produce unauthenticated network exposure:

1. Auth is opt-in and defaults to off (mcp_pinot/config.py:64,328):

@dataclass
class ServerConfig:
   ...
   oauth_enabled: bool = False
   ...

def load_server_config() -> ServerConfig:
   return ServerConfig(
       ...
       oauth_enabled=os.getenv("OAUTH_ENABLED", "false").lower() == "true",
       ...
   )

2. Auth construction is gated by oauth_enabled (mcp_pinot/server.py:26-46):

_auth = None
if server_config.oauth_enabled:
    oauth_config = load_oauth_config()
    token_verifier = JWTVerifier(...)
    _auth = OAuthProxy(...)

mcp = FastMCP("Pinot MCP Server", auth=_auth)

When oauth_enabled is false (default), _auth stays None and FastMCP registers all @mcp.tool endpoints with no authentication.

3. Default bind is all interfaces on a well-known port (mcp_pinot/config.py:60-61):

 host: str = "0.0.0.0"
port: int = 8080

The HTTP transport in server.py:263-268 uses these values directly. Any operator following the README's HTTP transport instructions (uv pip install, .env from .env.example, run) ends up with a network-reachable MCP server with no auth.

Confused-deputy

The Pinot client uses server-side credentials loaded from environment variables (mcp_pinot/config.py:285-294, 300-315). When an unauthenticated MCP caller invokes read_query or any other tool, the request is executed with the server's PINOT_TOKEN or PINOT_USERNAME/PINOT_PASSWORD, which is typically a privileged service account. The MCP server effectively launders the caller's lack of identity into the server's privileges against the upstream cluster.

Exposed tools

All 14 tools in…