ContextForge: DNS TOCTOU race condition causes SSRF protection bypass (`/admin/gateways/test`)

Summary

ContextForge is an AI gateway, registry, and proxy that provides centralized discovery, guardrails, and management for MCP, A2A, and REST or gRPC APIs. Prior to 1.0.3, the /admin/gateways/test call site in mcpgateway/admin.py calls validate_gateway_test_url() in mcpgateway/common/validators.py to resolve and reject private, loopback, link-local, and cloud-metadata addresses, but ResilientHttpClient later resolves the original hostname again without binding the validated address. When MCPGATEWAY_ADMIN_API_ENABLED is enabled, an attacker with a database-backed role containing explicit gateways.read permission can use DNS rebinding to return a public address during validation and a private or metadata address during connection, bypassing ssrf_blocked_networks and ssrf_dns_fail_closed because those controls apply only to the validation-time result. The endpoint's allow_admin_bypass=False setting means a bootstrap-only virtual platform-admin identity without a database role is not sufficient. Successful exploitation can reach internal services and cloud metadata, expose cloud credentials, access internal APIs, or probe internal network ports. This issue is fixed in version 1.0.3.

Timeline

1. Sep 14, 2026, 3:56 PM UTCCVE published
2. Sep 14, 2026, 4:33 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: no · Technical impact: partial

3. Sep 14, 2026, 4:33 PM UTCRecord last updated

Affected versions

• IBM mcp-context-forge

  fixed in 1.0.3

• IBM mcp-contextforge-gateway

  fixed in 1.0.3

• mcp-contextforge-gatewayPyPI

  fixed in 1.0.3

References 3