Description

IBM ContextForge MCP Gateway (`mcp-contextforge-gateway`) <= v1.0.6 MCP Context Forge could allow a remote authenticated attacker to obtain sensitive information due to a DNS rebinding vulnerability during tool invocation.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.7",
  "pubDate": "2026-09-04T16:17:21.517Z",
  "pubdate": "2026-09-04T16:17:21.517Z",
  "executiveSummary": "The IBM ContextForge MCP Gateway (mcp-contextforge-gateway) through version 1.0.6 is susceptible to a DNS rebinding vulnerability during tool invocation.\nThis vulnerability stems from improper validation of hostnames or IP addresses when the gateway resolves and fetches external resources during tool execution.\nA remote authenticated attacker can leverage this flaw to bypass same-origin policies or firewall restrictions by manipulating DNS resolution, effectively redirecting the gateway's requests to internal services or localhost.\nThe primary impact is the unauthorized disclosure of sensitive information residing within the internal network segment that is otherwise inaccessible to external entities.\nExploitation requires the attacker to be authenticated to the platform, after which they can orchestrate the DNS rebinding attack by controlling a malicious DNS server.\nThe vulnerability represents a significant risk to internal infrastructure, as it enables the gateway to be used as a proxy to exfiltrate data from protected backend services.\nOrganizations relying on the affected versions of the MCP Context Forge gateway should prioritize restricting network access and monitoring tool invocation patterns to identify anomalous DNS queries.",
  "technicalDetails": "The core of this vulnerability lies in the DNS resolution process employed by the mcp-contextforge-gateway during the execution of external tools. When the gateway processes a tool invocation that requires fetching or interacting with a remote resource, it fails to perform adequate verification of the target destination after the initial DNS resolution.\nIn a DNS rebinding attack scenario, the attacker provides an initial hostname that resolves to a benign IP address under the attacker's control, passing the gateway's initial validation checks. Once the gateway proceeds with the request, the attacker's authoritative DNS server responds with a very short Time-To-Live (TTL) value.\nSubsequently, when the gateway performs a secondary request to the same hostname, the attacker's DNS server provides an IP address pointing to an internal resource (e.g., 127.0.0.1 or an internal metadata service). Because the application does not re-validate the target IP against a whitelist, the request is forwarded to the internal service, bypassing intended network segmentation.\nThe attack flow proceeds as follows: 1) The attacker initiates an authenticated tool invocation containing the malicious URL. 2) The gateway resolves the hostname to the attacker's server, which provides a low-TTL response. 3) The gateway caches the result, but the attacker forces a resolution refresh. 4) The gateway resolves the hostname to an internal service endpoint. 5) The gateway executes the tool against the internal endpoint, capturing the sensitive response and returning it to the attacker through the tool invocation output.\nThis mechanism allows an authenticated attacker to perform Server-Side Request Forgery (SSRF) via DNS manipulation, potentially leading to the extraction of sensitive environment variables, configuration data, or internal API responses that are sensitive to the gateway's operational context.\nThe vulnerability affects all versions of mcp-contextforge-gateway up to and including v1.0.6. The flaw is inherent in the gateway's request-handling component, which lacks robust hostname/IP filtering, such as checks for private address ranges or loopback addresses after resolution. Because the attacker must be authenticated to trigger the vulnerable code path, the scope is limited to users with permission to execute tools through the gateway interface, though this is a significant threat in multi-tenant or collaborative environments."
}