CVE-2026-5832: atototo api-lab-mcp SSRF Vulnerability

CVE-2026-5832 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been identified in atototo api-lab-mcp versions up to 0.2.1. This security weakness affects multiple functions including analyze_api_spec, generate_test_scenarios, and test_http_endpoint within the src/mcp/http-server.ts file of the HTTP Interface component. By manipulating the source or url arguments, an unauthenticated remote attacker can induce the server to make arbitrary HTTP requests to internal or external destinations.

Critical Impact

Remote attackers can exploit this SSRF vulnerability to access internal services, bypass firewall restrictions, scan internal networks, or potentially exfiltrate sensitive data from systems that should not be publicly accessible.

Affected Products

• atototo api-lab-mcp versions up to and including 0.2.1
• Systems running the vulnerable HTTP Interface component
• Deployments with network access to internal services

Discovery Timeline

• 2026-04-09 - CVE-2026-5832 published to NVD
• 2026-04-09 - Last updated in NVD database

Technical Details for CVE-2026-5832

Vulnerability Analysis

This vulnerability falls under CWE-918 (Server-Side Request Forgery), a critical web application security flaw where an attacker can abuse server functionality to make HTTP requests to arbitrary destinations. The vulnerable functions in the api-lab-mcp HTTP Interface accept user-controlled URL parameters without adequate validation or sanitization.

The SSRF condition allows attackers to leverage the server as a proxy to reach internal services, cloud metadata endpoints, or other network resources that would otherwise be inaccessible from external networks. This is particularly dangerous in cloud environments where metadata services (such as AWS EC2 metadata at 169.254.169.254) can be queried to obtain credentials and sensitive configuration data.

The exploit has been publicly disclosed, meaning threat actors have access to the technical details needed to weaponize this vulnerability. The project maintainers were notified through an issue report but have not yet responded, leaving users without an official patch.

Root Cause

The root cause of this vulnerability lies in the inadequate input validation of the source and url parameters passed to the analyze_api_spec, generate_test_scenarios, and test_http_endpoint functions. The application fails to implement proper URL allowlisting, hostname validation, or protocol restrictions before initiating outbound HTTP requests. This allows attackers to specify arbitrary URLs, including those targeting internal network resources, localhost services, or cloud metadata endpoints.

Attack Vector

The vulnerability is exploitable remotely over the network without authentication. An attacker can craft malicious requests to the vulnerable HTTP Interface endpoints, supplying attacker-controlled URLs in the source or url parameters. When the server processes these requests, it will fetch content from the specified URL on behalf of the attacker.

The attack can be executed to perform internal network reconnaissance by probing internal IP ranges and ports, access cloud metadata services to steal credentials or configuration data, interact with internal APIs and services that lack authentication when accessed from trusted sources, and bypass IP-based access controls by leveraging the server's trusted network position.

Detection Methods for CVE-2026-5832

Indicators of Compromise

• Outbound HTTP requests from the api-lab-mcp server to internal IP addresses (e.g., 10.x.x.x, 172.16.x.x, 192.168.x.x)
• Requests targeting cloud metadata endpoints such as 169.254.169.254 or metadata.google.internal
• Unusual outbound connections to localhost (127.0.0.1) on various ports
• Requests to the vulnerable endpoints (analyze_api_spec, generate_test_scenarios, test_http_endpoint) containing suspicious URL parameters

Detection Strategies

• Monitor application logs for requests to the affected functions with external or internal IP addresses in URL parameters
• Implement network-level monitoring for unexpected outbound connections from the api-lab-mcp server
• Deploy web application firewalls (WAF) with SSRF detection rules to inspect and block malicious URL parameters
• Use intrusion detection systems to alert on traffic patterns consistent with SSRF exploitation

Monitoring Recommendations

• Enable verbose logging for the HTTP Interface component to capture all incoming requests and outbound connections
• Set up alerts for any requests containing private IP ranges or localhost references in URL parameters
• Monitor for connections to cloud provider metadata services from application servers
• Review access logs regularly for patterns indicating automated scanning or exploitation attempts

How to Mitigate CVE-2026-5832

Immediate Actions Required

• Restrict network access to the api-lab-mcp HTTP Interface to trusted sources only using firewall rules
• Implement network segmentation to limit the server's ability to reach sensitive internal resources
• Deploy a web application firewall with SSRF protection rules in front of the vulnerable application
• Consider disabling the affected functionality (analyze_api_spec, generate_test_scenarios, test_http_endpoint) if not critical to operations

Patch Information

At the time of publication, no official patch has been released by the project maintainers. The vulnerability was reported through a GitHub Issue, but the project has not yet responded. Users should monitor the api-lab-mcp repository for security updates and consider alternative solutions until a patch is available.

Additional technical details are available in the VulDB vulnerability entry and the public exploit report.

Workarounds

• Implement URL allowlisting at the application level to restrict outbound requests to known, trusted domains only
• Use network-level controls to block outbound connections from the api-lab-mcp server to internal IP ranges and metadata services
• Deploy a reverse proxy that validates and sanitizes URL parameters before forwarding requests to the application
• Consider running the application in an isolated network segment with no access to sensitive internal resources

# Example iptables rules to block SSRF to internal networks and metadata services
# Block access to private IP ranges
iptables -A OUTPUT -d 10.0.0.0/8 -m owner --uid-owner api-lab-user -j DROP
iptables -A OUTPUT -d 172.16.0.0/12 -m owner --uid-owner api-lab-user -j DROP
iptables -A OUTPUT -d 192.168.0.0/16 -m owner --uid-owner api-lab-user -j DROP

# Block access to cloud metadata services
iptables -A OUTPUT -d 169.254.169.254 -m owner --uid-owner api-lab-user -j DROP