Is This vulnerability exploited in the wild?

No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

How severe is This vulnerability?

Medium severity, with a CVSS score of 6.3, published 15 June 2026.

Which products and versions are affected?

Universal Tool Calling Protocol Python-Utcp 1.1.0; Universal Tool Calling Protocol Utcp-Gql <= 1.1.0; Universal Tool Calling Protocol Utcp-Websocket <= 1.1.0.

Is there a fix for This vulnerability?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is This vulnerability attacked?

It is attacked over the network, in a software library.

Check whether you run Universal Tool Calling Protocol Python-Utcp, Universal Tool Calling Protocol Utcp-Gql or Universal Tool Calling Protocol Utcp-Websocket at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

python-utcp localhost prefix validation bypass in utcp-gql and utcp-websocket

Q: Is there a fix for This vulnerability?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

Q: How is This vulnerability attacked?

It is attacked over the network, in a software library.

Q: Am I affected?

Check whether you run Universal Tool Calling Protocol Python-Utcp, Universal Tool Calling Protocol Utcp-Gql or Universal Tool Calling Protocol Utcp-Websocket at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Severity: medium · CVSS 6.3 · Published 2026-06-15

The python-utcp library provides GraphQL and WebSocket communication plugins for AI agents. A validation flaw allows attackers to bypass localhost-only security checks by crafting URLs with attacker domains that begin with "127.0.0.1" or "localhost" prefixes (e.g., "127.0.0.1.attacker.com"). This enables authenticated API requests to be sent to remote attacker-controlled servers, potentially exposing authorization headers, API keys, and sensitive tool-call data.

Technologies: Universal Tool Calling Protocol Python-Utcp, Universal Tool Calling Protocol Utcp-Gql, Universal Tool Calling Protocol Utcp-Websocket. Vendors: Universal Tool Calling Protocol.

Quick answers

Is This vulnerability exploited in the wild?: No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?: Medium severity, with a CVSS score of 6.3, published 15 June 2026.
Which products and versions are affected?: Universal Tool Calling Protocol Python-Utcp 1.1.0; Universal Tool Calling Protocol Utcp-Gql <= 1.1.0; Universal Tool Calling Protocol Utcp-Websocket <= 1.1.0.
Is there a fix for This vulnerability?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is This vulnerability attacked?: It is attacked over the network, in a software library.
Am I affected?: Check whether you run Universal Tool Calling Protocol Python-Utcp, Universal Tool Calling Protocol Utcp-Gql or Universal Tool Calling Protocol Utcp-Websocket at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

This vulnerability is a server-side request forgery (SSRF) caused by improper hostname validation in the GraphQLCommunicationProtocol._enforce_https_or_localhost() and WebSocketCallTemplate.validate_url() methods. The affected components use string prefix matching instead of parsing and validating the actual hostname, allowing URLs such as "http://127.0.0.1.attacker.com" or "http://127.0.0.1.x.x.x.sslip.io" to pass localhost validation despite resolving to remote servers. The attack requires influence over endpoint URL configuration or the ability to control which URL is used for connections. An authenticated attacker can exploit this to redirect requests to attacker infrastructure and harvest sensitive data like authorization headers, API keys, and tool-call payloads. No patched version is currently available.

Affected products

universal-tool-calling-protocol utcp-gql <= 1.1.0
universal-tool-calling-protocol utcp-websocket <= 1.1.0
universal-tool-calling-protocol python-utcp 1.1.0

Timeline

2026-06-08: disclosed: Vulnerability reported via GitHub issue #86
2026-06-15: advisory: GHSA-vg9f-q4xh-62r4 published; duplicate advisory withdrawn on 2026-08-25

References

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