Executive Summary

CVE-2026-7221 is a Server-Side Request Forgery (SSRF) vulnerability found in TencentCloudBase CloudBase-MCP up to version 2.17.0. It affects the openUrl function in the file mcp/src/interactive-server.ts, specifically the open-url API endpoint.

The vulnerability arises because the server accepts a user-controlled URL parameter (req.body.url) without proper validation and uses it to make outbound requests. This allows an attacker to coerce the server into making requests to arbitrary internal or external network resources.

The exploit can be launched remotely since the vulnerable endpoint listens on all network interfaces by default (0.0.0.0), exposing it beyond localhost.

The fix involves adding strict URL validation to block unsafe URLs (such as localhost, private IP ranges, link-local addresses, and cloud metadata endpoints), changing the default server binding to localhost (127.0.0.1) to restrict access, and rejecting unsafe requests with HTTP 403 Forbidden.

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Impact Analysis

This SSRF vulnerability can impact you by allowing attackers to make the vulnerable server perform unauthorized requests to internal or external network resources.

• Confidentiality impact: Attackers may access sensitive internal services or metadata endpoints, potentially leaking confidential information.
• Integrity impact: Attackers can influence outbound requests but cannot directly modify server data, so integrity impact is low.
• Availability impact: Repeated exploitation could cause resource exhaustion or unwanted behavior, but availability impact is low.

The vulnerability has a CVSS v3.1 base score of 7.3 to 9.3 depending on exposure, indicating a high to critical severity if the server is exposed to untrusted networks.

If the vulnerable server is exposed to untrusted networks without authentication or URL validation, attackers can exploit this remotely to access internal systems or cause other security issues.

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Detection Guidance

This vulnerability can be detected by checking if the vulnerable CloudBase-MCP server is exposing the /api/open-url HTTP POST endpoint without URL validation or access restrictions.

One practical detection method is to send a crafted POST request to the /api/open-url endpoint with a URL parameter pointing to a controlled listener and observe if the server makes an outbound request.

Example command using curl to test if the server opens a URL without validation:

• curl -X POST http://<target-host>:<port>/api/open-url -H "Content-Type: application/json" -d '{"url":"http://127.0.0.1:8765/"}'

If the server responds with success and the attacker-controlled listener receives a request, it confirms the vulnerability.

Additionally, verify the server's binding address. If it is bound to 0.0.0.0 (all interfaces), it is more exposed and vulnerable to remote exploitation.

Checking the version of CloudBase-MCP is also important, as versions up to 2.17.0 are vulnerable.

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Mitigation Strategies

The primary immediate mitigation is to upgrade CloudBase-MCP to version 2.17.1 or later, which includes the patch that enforces strict URL validation and restricts server binding.

If upgrading immediately is not possible, apply the following mitigations:

• Restrict the server binding address by setting the environment variable INTERACTIVE_SERVER_HOST=127.0.0.1 to limit access to localhost only.
• Avoid exposing or port-forwarding the interactive server to untrusted networks.
• Implement authentication and authorization controls on the /api/open-url endpoint to prevent unauthorized access.
• Manually review and enforce URL allowlists or validation to block unsafe URLs, including loopback, link-local, private IP ranges, and cloud metadata endpoints.

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Compliance Impact

The vulnerability CVE-2026-7221 is a Server-Side Request Forgery (SSRF) issue that allows an attacker to make the affected server send unauthorized requests to internal or external systems. This can lead to potential leakage of sensitive information, which impacts confidentiality.

Since the vulnerability can expose internal network resources and potentially sensitive data, it may affect compliance with data protection regulations such as GDPR and HIPAA, which require safeguarding personal and sensitive information against unauthorized access or disclosure.

Organizations using the affected TencentCloudBase CloudBase-MCP component should consider this vulnerability a risk to their compliance posture, especially if the server is exposed to untrusted networks without proper access controls, authentication, or URL validation.

Mitigations such as restricting server binding to localhost, implementing strict URL validation, and enforcing authentication can help reduce the risk and support compliance with these standards.

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