A critical Server-Side Request Forgery vulnerability in the mcp-use inspector proxy allows unauthenticated attackers to access sensitive internal network services and data.

This is a Server-Side Request Forgery (CWE-918) vulnerability located in the mountMcpProxy function. An unauthenticated attacker can supply a malicious URL via the X-Target-URL header or the __mcp_target parameter to force the server to make requests to internal loopback, link-local, or private network addresses.

The ability for an unauthenticated attacker to scan and interact with internal network resources poses a severe risk to organizational infrastructure. With a CVSS score of 8.6, this flaw could lead to the exposure of sensitive configuration data, unauthorized access to internal APIs, or the compromise of local services that rely on implicit trust.

Immediate Action: Upgrade to a version of mcp-use that includes the fix for this SSRF vulnerability, as identified in the vendor security advisory. If a patch is not yet available, restrict access to the inspector proxy to trusted IP addresses only.

Proactive Monitoring: Monitor server access logs for anomalous requests containing the X-Target-URL header or the __mcp_target parameter pointing to internal IP ranges. Alert on any outbound connection attempts originating from the proxy server directed at internal RFC1918 addresses.

Compensating Controls: Deploy a Web Application Firewall (WAF) to inspect and block incoming requests that attempt to pass unauthorized values through the identified header and parameter fields.

Public Exploit Available: Unknown

Given the high CVSS score and the potential for unauthenticated remote access to internal resources, this vulnerability should be treated as a priority. Administrators must audit their network exposure and apply the vendor-provided patch as soon as it is released to prevent unauthorized internal data exfiltration or service interaction.