CVE-2026-53708 in MCP Context Forge
Summary
by MITRE • 09/14/2026
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.
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Analysis
by VulDB Data Team • 09/14/2026
ContextForge operates as an AI gateway, registry, and proxy designed to provide centralized discovery, guardrails, and management for Model Context Protocol (MCP), A2A, and REST or gRPC APIs. The security architecture relies heavily on server-side request forgery protections to prevent unauthorized access to internal resources. Specifically, the system implements validation logic within the /admin/gateways/test endpoint located in mcpgateway/admin.py. This call site invokes validate_gateway_test_url from mcpgateway/common/validators.py with the intent of resolving and rejecting URLs that point to private IP ranges, loopback addresses, link-local networks, or cloud metadata endpoints. The underlying assumption is that by validating the hostname at the time of request initiation, subsequent network connections will remain confined to safe external destinations.
However, a critical implementation flaw exists in how this validation interacts with the actual HTTP client used for making requests. While validate_gateway_test_url performs DNS resolution and checks the resulting IP address against blocked networks, it does not enforce that restriction on the connection itself. The ResilientHttpClient component subsequently resolves the original hostname again to establish the network connection. This second resolution step occurs independently of the initial validation check. Because there is no binding between the validated safe address and the actual socket connection, an attacker can exploit DNS rebinding techniques. By controlling a domain name used in the request, the attacker can configure their authoritative DNS server to return different IP addresses for successive queries. The first query returns a public, allowed IP address that passes the validation filter. The second query, made by ResilientHttpClient during connection establishment, returns a private or cloud metadata IP address.
This race condition effectively bypasses the ssrf_blocked_networks and ssrf_dns_fail_closed security controls because these mechanisms only inspect the result of the initial validation-time DNS resolution. They do not monitor or restrict the final destination used for data transmission. Consequently, if an attacker possesses a database-backed role with explicit gateways.read permission and has MCPGATEWAY_ADMIN_API_ENABLED set to true, they can craft requests that appear valid during inspection but connect to internal services upon execution. The allow_admin_bypass=False setting ensures that bootstrap-only virtual platform-admin identities without persistent database roles cannot exploit this flaw directly through administrative bypass mechanisms, requiring the attacker to have legitimate application-level permissions first.
The operational impact of this vulnerability is severe, as it allows for Server-Side Request Forgery attacks against internal infrastructure and cloud environments. Successful exploitation enables an authenticated user with specific read privileges to reach sensitive internal services that are not exposed to the public internet. Attackers can access cloud metadata endpoints such as those found in AWS EC2 or Azure Managed Identity services to retrieve temporary security credentials, potentially leading to full compromise of cloud resources. Additionally, the vulnerability facilitates reconnaissance activities against internal APIs and allows for probing of internal network ports, expanding the attack surface significantly beyond what was originally intended by the application's design.
To mitigate this risk, organizations must upgrade ContextForge to version 1.0.3 or later, where the validation logic has been corrected to ensure that DNS resolution is consistent between the security check and the actual connection attempt. Until an update is applied, administrators should consider restricting access to the /admin/gateways/test endpoint using network-level controls such as firewalls or reverse proxy rules if possible. It is also advisable to audit user roles to ensure that only trusted personnel hold gateways.read permissions when administrative API features are enabled. This vulnerability aligns with CWE-918, which addresses Server-Side Request Forgery flaws resulting from improper validation of dynamic input, and maps to MITRE ATT&CK technique T1557, specifically Adversary-in-the-Middle or Lateral Movement via cloud metadata services if credentials are harvested.