universal-tool-calling-protocol/python-utcp

A vulnerability was detected in universal-tool-calling-protocol python-utcp 1.1.0. This affects an unknown function of the component utcp-gql/utcp-websocket. Performing a manipulation results in server-side request forgery. The attack can be initiated remotely. The exploit is now public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

python-utcp is the python implementation of UTCP. Prior to 1.1.3, the _substitute_utcp_args method in cli_communication_protocol.py inserts user-controlled tool_args values directly into shell command strings without any sanitization or escaping. These commands are then executed via /bin/bash -c (Unix) or powershell.exe -Command (Windows), allowing an attacker to inject arbitrary shell commands. This vulnerability is fixed in 1.1.3.

python-utcp is the python implementation of UTCP. Prior to 1.1.3, _prepare_environment() in cli_communication_protocol.py passes a full copy of os.environ to every CLI subprocess. When combined with CVE-2026-45369, an attacker can exfiltrate all process-level secrets in a single tool call. This vulnerability is fixed in 1.1.3.

python-utcp is the python implementation of UTCP. Prior to 1.1.3, the utcp-http plugin is vulnerable to a blind Server-Side Request Forgery (SSRF) caused by a trust-boundary inconsistency between manual discovery and tool invocation. register_manual() validates the discovery URL against an HTTPS / loopback allowlist, but call_tool() and call_tool_streaming() reuse the resolved tool_call_template.url directly without revalidating, and the OpenAPI converter blindly trusts whatever servers[0].url an attacker-hosted spec declares. An attacker who hosts a malicious OpenAPI spec on a legitimate HTTPS endpoint can declare e.g. servers: [{ url: "http://127.0.0.1:9090" }] or servers: [{ url: "http://169.254.169.254" }]; the OpenAPI converter then produces tools whose URL points at internal services on the agent host. All three HTTP-class protocols (utcp_http.http, utcp_http.streamable_http, utcp_http.sse) shared the same gap. This vulnerability is fixed in 1.1.3.

The vulnerability arises when a client fetches a tools’ JSON specification, known as a Manual, from a remote Manual Endpoint. While a provider may initially serve a benign manual (e.g., one defining an HTTP tool call), earning the clients’ trust, a malicious provider can later change the manual to exploit the client.