---
id: "CVE-2026-8355"
kind: "vulnerability"
aliases: ["CVE-2026-8355"]
title: "IBM ContextForge MCP Gateway: OAuth token URL allows server-side request forgery"
severity: "medium"
cvss: 5.4
epss: null
exploited: false
status: "open"
category: "ai-tooling"
products: []
ecosystems: []
tags: ["ai-tooling", "cloud", "ibm-contextforge", "mcp", "self-hosted"]
not_affected_if: ["no-gateway-creation-users", "no-oauth-gateway-registration", "version-outside-0.1.0-to-1.0.5"]
published_at: "2026-10-20T00:19:20+00:00"
first_seen_at: "2026-10-23T21:57:19+00:00"
updated_at: "2026-10-25T04:16:43+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-8355", "first_seen_at": "2026-10-23T21:57:19+00:00"}]
---

# IBM ContextForge MCP Gateway: OAuth token URL allows server-side request forgery

IBM ContextForge MCP Gateway versions 0.1.0 through 1.0.5 do not validate the oauth_config.token_url field when registering a gateway with OAuth client credentials. An authenticated user with gateway creation rights can make the server send HTTP POST requests, including form-encoded credentials, to internal services or cloud metadata endpoints and read up to 256 characters of the response back.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed ContextForge MCP Gateway version against the affected range 0.1.0 through 1.0.5.
- Review whether gateway registration with oauth_config is enabled for users who hold gateway creation privileges.
- unknown for other exposure details the sources do not give.

## Fix

- Upgrade IBM ContextForge MCP Gateway to a release later than 1.0.5 (the fixed version is not named in the sources; unknown).
- Restrict gateway creation privileges to trusted users until upgraded.
- Block the gateway host's outbound access to cloud metadata endpoints and internal networks as a mitigation.

## Timeline

- 2026-10-23T21:57:19+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-8355

## From the sources

IBM ContextForge MCP Gateway 0.1.0 through 1.0.5 is vulnerable to a server-side request Forgery (SSRF) that allows authenticated users with gateway creation privileges to perform arbitrary HTTP POST requests to internal network resources and cloud metadata endpoints. The vulnerability occurs during OAuth-enabled gateway registration when the system fails to validate the oauth_config.token_url parameter. When registering a gateway with OAuth client credentials authentication, an attacker can supply a malicious token_url pointing to internal services, cloud metadata endpoints (AWS IMDSv1, GCP, Azure), or localhost-bound services. The application immediately performs an HTTP POST request to the attacker-controlled URL with form-encoded credentials in the body. If the response cannot be parsed as a valid OAuth token response, up to 256 characters of the response body are reflected back to the attacker in the HTTP 502 error message. This vulnerability bypasses existing SSRF protections that are applied to the gateway.url field but not to OAuth configuration parameters.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_