MCP StreamableHTTPTransport DNS Rebinding Vulnerability and Fix

Vulnerability Overview This vulnerability involves insufficient protection against DNS rebinding attacks. Specifically, has a flaw in validating the and headers, which could lead to DNS rebinding attacks. Attackers can bypass existing security mechanisms by constructing specific and headers, thereby launching attacks against the local MCP server. Impact Scope Affected Component: Attack Type: DNS rebinding attack Potential Risk: Attackers can exploit this vulnerability to launch attacks against the local MCP server, potentially resulting in data leakage or other security issues. Remediation Plan 1. Enable DNS Rebinding Protection by Default: - Enable DNS rebinding protection by default in . - Enable the protection by setting . 2. Validate and Headers: - Verify that the header matches the default allowed local hosts (such as , , ) or the complete value. - Verify that the header belongs to the same origin or is an explicitly allowed source. 3. Provide Configuration Options: - Provide and configuration options, allowing users to customize the allowed and values. - If deployed behind a reverse proxy or bound to a non-loopback interface, these lists need to be relaxed. 4. Disable Protection: - If upstream proxies or middleware have already validated these headers, the protection can be disabled by setting . Proof of Concept (POC) Code The following code snippet demonstrates how to configure and validate the and headers: Summary This vulnerability is prevented by validating and headers to mitigate DNS rebinding attacks. The remediation plan includes enabling protection by default, validating header values, providing configuration options, and allowing the protection to be disabled. The related code snippet demonstrates how to implement these validation logic mechanisms.

Goal Reached Thanks to every supporter — we hit 100%!

MCP StreamableHTTPTransport DNS Rebinding Vulnerability and Fix

More from this source