---
id: CVE-2026-101058
title: >-
  python-utcp (pip package utcp-http) before 1.1.12 does not verify whether tool
  URLs declared in a hand-written UTCP manual point at the agent's own loopback
  interface when that manual is discovered from a remote, non-loopback origin
summary: >-
  python-utcp (pip package utcp-http) before 1.1.12 does not verify whether tool
  URLs declared in a hand-written UTCP manual point at the agent's own loopback
  interface when that manual is discovered from a remote, non-loopback origin.
  Bec…
severity: medium
cvss: 6.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N'
cwe:
  - CWE-918
vendor: universal-tool-calling-protocol
product: python-utcp
affected:
  - python-utcp < 1.1.12
published: '2026-09-27'
updated: '2026-09-27'
sourceUpdated: '2026-09-27T18:16:31.973'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-101058'
references:
  - url: >-
      https://github.com/universal-tool-calling-protocol/python-utcp/security/advisories/GHSA-8vxx-v7r9-948g
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/python-utcp-before-1.1.12-ssrf-via-remote-http-manual
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-27T17:56:02.210Z'
---

## Overview

python-utcp (pip package utcp-http) before 1.1.12 does not verify whether tool URLs declared in a hand-written UTCP manual point at the agent's own loopback interface when that manual is discovered from a remote, non-loopback origin. Because ensure_secure_url intentionally permits loopback HTTP for local development and native manuals bypassed the loopback check performed by the OpenAPI converter, an attacker who can serve a UTCP manual that a victim registers can cause the client to issue requests to services bound only to 127.0.0.1 on the victim host and have the response bodies returned to the caller (server-side request forgery). The http, sse and streamable_http protocols are all affected. Reach is limited to loopback, and exploitation further requires a loopback service that answers unauthenticated requests with useful data. Fixed in utcp-http 1.1.12, which rejects manuals fetched from a non-loopback origin that declare loopback tool URLs, keyed off the final post-redirect discovery URL.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.