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MEDIUM severity

CVE-2026-44661 — utcp-http

MEDIUM

CVE-2026-44661 is a medium-severity (CVSS 4.7) Server-Side Request Forgery (SSRF) vulnerability in utcp-http. A fix is available for utcp-http — see the affected versions and patch details below.

utcp-http vulnerable to SSRF via attacker-controlled OpenAPI servers[0].url in HTTP communication protocol

Also known asPYSEC-2026-3396
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44661.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs7th percentile — riskier than 7% of all scored CVEsHighest risk
0.00%0.23%0.46%0.70%0.0%0.2%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐍utcp-http

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

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. An attacker who hosts a malicious OpenAPI spec on a legitimate HTTPS endpoint can declare servers: [{ url: "http://169.254.169.254" }] (or any internal address) in the spec; the OpenAPI converter blindly trusts that value and the tool becomes a blind SSRF primitive that exposes cloud metadata, internal services, and other firewalled-only endpoints to the LLM caller.

All three HTTP-class protocols (utcp_http.http, utcp_http.streamable_http, utcp_http.sse) shared the same gap, plus a separate prefix-bypass: the previous startswith("http://localhost") check let URLs like http://localhost.evil.com through.

Impact

A remote attacker who can convince the agent (via the LLM context, prompt injection, or a tool-discovery surface) to register their HTTPS OpenAPI URL can:

  • Map internal networks behind the agent.
  • Read AWS/GCP IAM credentials from cloud metadata endpoints (http://169.254.169.254, http://metadata.google.internal).
  • Reach unauthenticated internal services (Elasticsearch, Redis HTTP, internal admin panels).
  • Have responses returned to the LLM, which combined with prompt injection enables exfiltration back to the attacker.

Affected versions

utcp-http <= 1.1.1.

Patched versions

utcp-http 1.1.2.

Patch

Commit: 5b16e43 on dev.

  • New utcp_http._security helper: ensure_secure_url(url, context=...) parses the URL with urllib.parse.urlparse and validates the hostname (not a string prefix) against the loopback set, closing the localhost.evil.com bypass.
  • All three protocols call ensure_secure_url(url, context="manual discovery") in register_manual (replacing the duplicated prefix check) and ensure_secure_url(url, context="tool invocation") immediately before each aiohttp request in call_tool / call_tool_streaming. The runtime check is the actual SSRF fix.
  • New regression tests in test_security.py pin the accept/reject decisions and explicitly cover the historical bypass cases.

Workarounds

For users who cannot upgrade immediately:

  • Refuse to call register_manual with any URL controlled by an untrusted party, even over HTTPS.
  • Restrict outbound network access from the host running the agent so internal addresses (RFC1918, 169.254.0.0/16, loopback for cloud metadata) are unreachable.

Credit

Discovered and reported by @YLChen-007 in #83.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIutcp-httpall versions1.1.2pip install --upgrade 'utcp-http==1.1.2'

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for utcp-http, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update utcp-http to 1.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44661 is resolved across your whole dependency graph.

  3. Workarounds

    Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

## Summary 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. An attacker who hosts a malicious OpenAPI spec on a legitimate HTTPS endpoint can declare `servers: [{ url: "http://169.254.169.254" }]` (or any internal address) in the spec; the OpenAPI converter blindly trus
O3 Security · Impact-Aware SCA

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CVE-2026-44661: utcp-http SSRF — Fixed in 1.1.2