Description

IBM ContextForge MCP Gateway could allow a remote authenticated attacker to obtain sensitive information due to server-side request forgery via DNS rebinding.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.2",
  "pubDate": "2026-09-04T16:17:59.550Z",
  "pubdate": "2026-09-04T16:17:59.550Z",
  "executiveSummary": "The IBM ContextForge MCP Gateway is susceptible to a Server-Side Request Forgery (SSRF) vulnerability facilitated by DNS rebinding.\nThis vulnerability allows a remote, authenticated attacker to bypass intended network access restrictions and interact with internal resources, services, or metadata endpoints that are typically inaccessible from the external network.\nThe risk involves the unauthorized disclosure of sensitive information, potential interaction with internal APIs, and the ability to leverage the gateway as a proxy for malicious requests directed at internal infrastructure.\nExploitation requires the attacker to hold authenticated access to the target system, from which they can manipulate DNS resolution to redirect requests originally intended for legitimate domains to arbitrary, restricted internal IP addresses.\nThe impact is significant, as it grants the attacker a foothold to probe internal network topography, exfiltrate data, or potentially perform unauthorized actions against service-side infrastructure.",
  "technicalDetails": "The vulnerability resides in the request handling logic of the IBM ContextForge MCP Gateway, specifically where the service processes user-supplied URLs or external inputs without implementing adequate validation or pinning of the resolved IP addresses.\nThe root cause is a failure to mitigate DNS rebinding attacks during the server-side request initiation process. DNS rebinding occurs when an attacker controls a malicious DNS server and provides a short Time-To-Live (TTL) for a domain record.\nIn the first stage of the attack, the gateway performs a DNS lookup for the attacker-controlled domain. The DNS server responds with a legitimate public IP address, which passes initial validation checks performed by the application logic.\nFollowing the initial validation, the attacker rapidly updates the DNS record to point to an internal or sensitive IP address (e.g., 127.0.0.1, 169.254.169.254, or internal network subnets).\nBecause the gateway relies on the host resolution provided at the time of the initial request validation rather than strictly controlling the destination through allow-listing or network segmentation, subsequent requests sent by the gateway are routed to the target internal service.\nThe attack flow proceeds as follows: 1) The attacker initiates an authenticated request to the gateway, providing a controlled URL. 2) The gateway resolves the domain to a benign IP to pass security checks. 3) The DNS TTL expires, and the gateway attempts to fetch the resource, resolving the domain to the target internal asset. 4) The gateway performs the request, acting as a proxy, and returns the response (or the outcome of the request) to the attacker.\nThis behavior allows the attacker to perform blind or non-blind SSRF. In non-blind scenarios, the attacker receives content from the internal service, leading to information disclosure. In blind scenarios, the attacker can verify the existence of internal services or trigger state-changing operations within the internal environment, effectively bypassing firewall rules and access control lists that assume the gateway is a trusted source."
}