CVE-2025-56404

Executive Summary

CVE-2025-56404 is a security advisory affecting MariaDB MCP (Management Control Plane) version 0.1.0. The vulnerability resides in the Server-Sent Events (SSE) service, which lacks proper user validation. This allows an unauthenticated attacker to gain sensitive information by connecting to the SSE endpoint. The vulnerability has a CVSS score of 0.0 (likely unassigned or placeholder), but the impact is considered high due to the potential exposure of internal system data, configuration details, or credentials. No public proof-of-concept (PoC) or exploit code is available at this time. The vendor has not released a patch.

Supply Chain & Package Security

This vulnerability is not related to a package manager (NPM, PyPI, Go, Ruby). It is a standalone application (MariaDB MCP) that may be deployed as part of a larger MariaDB infrastructure. Organizations using MariaDB MCP 0.1.0 should treat this as a critical supply chain risk due to the lack of authentication on the SSE service.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unassigned)
• Attack Vector (AV): Network (likely)
• Attack Complexity (AC): Low (likely)
• Privileges Required (PR): None
• User Interaction (UI): None
• Scope (S): Unchanged (likely)
• Confidentiality (C): High (likely)
• Integrity (I): None (likely)
• Availability (A): None (likely)

Threat Level: High. The vulnerability allows unauthenticated access to sensitive information via the SSE service. This could lead to data exfiltration, reconnaissance, or further exploitation.

Deep Dive & Mechanics

The MariaDB MCP (Management Control Plane) is a component used for managing MariaDB instances. It includes a Server-Sent Events (SSE) service, which is a standard mechanism for pushing real-time updates to clients. The vulnerability arises because the SSE endpoint does not enforce any authentication or authorization checks. An attacker who can reach the MCP service (typically on a network port) can connect to the SSE endpoint and receive all events broadcast by the service.

These events may include:

• System configuration details
• Database connection strings
• Credentials (e.g., usernames, passwords, API keys)
• Internal network information
• Logs or error messages

The lack of user validation means that any client, regardless of identity, can subscribe to the SSE stream. This is a classic case of missing authentication on a sensitive endpoint.

Vulnerable vs. Patched Code

Vulnerable Code (MariaDB MCP 0.1.0): The SSE endpoint is likely implemented without any authentication middleware. Example (pseudo-code):

// Vulnerable: No authentication check
app.get('/sse', (req, res) => {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    'Connection': 'keep-alive'
  });
  // Send events without verifying user identity
  sendEvents(res);
});

Patched Code (Hypothetical): A patched version would require authentication before allowing SSE connections:

// Patched: Authentication required
app.get('/sse', authenticate, (req, res) => {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    'Connection': 'keep-alive'
  });
  sendEvents(res);
});

function authenticate(req, res, next) {
  // Validate token, session, or API key
  if (!req.headers.authorization) {
    return res.status(401).send('Unauthorized');
  }
  next();
}

Exploitation & Lab Setup

Red Team (Attacker)

1. Reconnaissance: Identify MariaDB MCP instances on the network. The SSE service typically runs on a specific port (e.g., 8080 or 8443). Use Shodan or Nmap to find exposed services.
2. Exploitation: Connect to the SSE endpoint using a simple HTTP client:

   curl -N http://target:port/sse
   

   Or using a WebSocket/SSE client:

   const eventSource = new EventSource('http://target:port/sse');
   eventSource.onmessage = (event) => {
     console.log('Received:', event.data);
   };
   

3. Data Exfiltration: Monitor the SSE stream for sensitive information. Save the output to a file for analysis.

Blue Team (Defender)

1. Detection: Monitor network traffic for connections to the SSE endpoint. Look for unusual patterns or large amounts of data being streamed.
2. Mitigation: Implement network segmentation to restrict access to the MCP service. Use a reverse proxy (e.g., Nginx) to add authentication:

   location /sse {
     auth_basic "Restricted";
     auth_basic_user_file /etc/nginx/.htpasswd;
     proxy_pass http://mcp_backend;
   }
   

3. Honeypot: Deploy a fake SSE endpoint to detect scanning or exploitation attempts.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Connections to */sse endpoint on MariaDB MCP ports (e.g., 8080, 8443)
  • Unusual HTTP headers (e.g., Accept: text/event-stream)
  • Large volumes of data being streamed from the MCP service
• File IOCs:
  • Logs containing GET /sse requests from unknown IPs
  • Configuration files with exposed credentials
• Behavioral IOCs:
  • Unauthorized access to the MCP service
  • Data exfiltration via SSE stream

Detection Engineering

YARA Rule

rule CVE_2025_56404_SSE_Exposure {
  meta:
    description = "Detects MariaDB MCP SSE service exposure"
    author = "Valters IT"
    date = "2025-04-10"
    reference = "CVE-2025-56404"
  strings:
    $sse_path = "/sse"
    $sse_header = "text/event-stream"
    $mcp_string = "MariaDB MCP"
  condition:
    any of them
}

Sigma Rule

title: MariaDB MCP SSE Service Unauthenticated Access
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects unauthenticated access to MariaDB MCP SSE endpoint
author: Valters IT
date: 2025/04/10
references:
  - CVE-2025-56404
logsource:
  category: webserver
  product: apache
  service: access_log
detection:
  selection:
    cs-method: 'GET'
    cs-uri-stem: '/sse'
  condition: selection
falsepositives:
  - Legitimate internal monitoring tools
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-56404 MariaDB MCP SSE Unauthenticated Access"; flow:to_server; content:"GET"; http_method; content:"/sse"; http_uri; content:"text/event-stream"; http_accept; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:
   • Disable the SSE service if not required.
   • Restrict network access to the MCP service using firewalls or ACLs.
   • Implement authentication (e.g., API keys, OAuth) on the SSE endpoint.
2. Long-term Fix:
   • Apply vendor patch when available.
   • Upgrade to a patched version of MariaDB MCP.
3. Compensating Controls:
   • Use a reverse proxy (e.g., Nginx, Apache) to add authentication.
   • Monitor logs for unauthorized access attempts.
   • Conduct regular security assessments.

Valters IT
Securing Digital Frontiers