CVE-2026-101057

What it is

utcp-mcp (the MCP plugin of python-utcp) through 1.1.2 connects to the HTTP and WebSocket MCP server URLs given in a call template's mcpServers configuration without the ensure_secure_url validation that the HTTP-family plugins apply, so the HTTPS/WSS-or-loopback rule is not enforced. A call template naming a plain-HTTP, non-loopback MCP server URL is dialed as configured, exposing the MCP handshake to network interception and permitting cleartext connections to internal hosts. The mcpServers configuration is operator-authored rather than remote data, and the connection is an MCP handshake rather than an arbitrary request returning a body, which limits practical exploitation; the OAuth2 token_url credential path described in the original report was not reachable in the affected versions, because the OAuth2 handler was never invoked and the call template's auth field was not read. Fixed in utcp-mcp 1.1.3, which validates server URLs before any connection is made.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. Limited direct impact.

Exploit odds

0.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-09-27 18:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-30 17:32 UTC Last updatedMost recent change to the record

Details

Published

2026-09-27 18:16 UTC

Last modified

2026-09-30 17:32 UTC

Exploit probability

0.1% · EPSS, next 30 days

Weakness

CWE-319 · Cleartext transmission

Record status

Deferred

Attack profile CVSS 4.0 · 2.3

Attack vector

Network

Complexity

High

Attack requirements

Present

Privileges needed

None

User interaction

Passive

Confidentiality

Low

Integrity

None

Availability

None