CVE-2025-56404: MariaDB MCP Information Disclosure Flaw

CVE-2025-56404 Overview

CVE-2025-56404 is an information disclosure vulnerability discovered in MariaDB Model Context Protocol (MCP) version 0.1.0. The vulnerability exists in the Server-Sent Events (SSE) service, which lacks proper user validation, allowing unauthenticated attackers to gain access to sensitive information transmitted through the service.

Critical Impact

Attackers can exploit the missing authentication in the SSE service to intercept and access sensitive data without requiring any credentials or user interaction.

Affected Products

• MariaDB Model Context Protocol 0.1.0

Discovery Timeline

• 2025-09-10 - CVE-2025-56404 published to NVD
• 2025-09-17 - Last updated in NVD database

Technical Details for CVE-2025-56404

Vulnerability Analysis

This vulnerability is classified as an Improper Input Validation issue (CWE-20), though it fundamentally represents an authentication bypass in the SSE service component. The SSE (Server-Sent Events) service in MariaDB MCP 0.1.0 fails to implement proper user validation mechanisms before serving event data to clients.

The vulnerability allows network-based attackers to access the SSE service without authentication. This results in potential exposure of sensitive information that flows through the event streaming mechanism. The attack requires no privileges, no user interaction, and can be executed remotely over the network with low complexity.

Root Cause

The root cause of this vulnerability lies in the absence of user validation controls within the SSE service implementation. When the SSE service receives incoming connection requests, it fails to verify whether the connecting client has proper authorization to access the event stream. This missing authentication check allows any network-accessible attacker to establish a connection and receive sensitive data intended only for authorized users.

Attack Vector

The vulnerability is exploitable over the network by any unauthenticated attacker who can reach the SSE service endpoint. An attacker can simply connect to the SSE service without providing any credentials and begin receiving sensitive information that is being streamed through the service.

The attack flow involves:

1. An attacker identifies a MariaDB MCP 0.1.0 instance with an exposed SSE service
2. The attacker establishes a direct connection to the SSE endpoint
3. Without any authentication challenge, the SSE service begins streaming event data to the attacker
4. The attacker receives sensitive information that should be restricted to authorized users only

For technical details regarding the vulnerability mechanism, refer to the MariaDB MCP GitHub Issue or the CVE Proof of Concept Discussion.

Detection Methods for CVE-2025-56404

Indicators of Compromise

• Unusual or unauthorized connections to the SSE service endpoints from unknown IP addresses
• Increased SSE connection volume from external or suspicious sources
• Authentication logs showing SSE access without corresponding user authentication events
• Network traffic analysis revealing SSE data streams to unauthorized destinations

Detection Strategies

• Monitor SSE service access logs for connections that lack associated authentication tokens or sessions
• Implement network intrusion detection rules to identify SSE protocol traffic from untrusted sources
• Deploy application-level monitoring to detect SSE endpoint access patterns inconsistent with normal user behavior
• Audit SSE service configurations to identify instances running vulnerable version 0.1.0

Monitoring Recommendations

• Enable detailed logging on SSE service endpoints to capture all connection attempts and client metadata
• Configure alerts for SSE connections originating from IP addresses not associated with authenticated users
• Implement network segmentation monitoring to detect unauthorized access attempts to internal SSE services
• Regularly review and audit SSE service access patterns against baseline normal activity

How to Mitigate CVE-2025-56404

Immediate Actions Required

• Identify all instances of MariaDB Model Context Protocol version 0.1.0 in your environment
• Restrict network access to SSE service endpoints using firewall rules or network segmentation
• Implement reverse proxy authentication in front of SSE endpoints as a compensating control
• Monitor SSE service connections for unauthorized access attempts while awaiting a patch

Patch Information

At the time of publication, no official vendor patch has been announced. Organizations should monitor the MariaDB MCP GitHub repository for security updates and patch releases. Upgrading to a patched version when available is the recommended remediation.

Workarounds

• Deploy a reverse proxy with authentication enforcement in front of the SSE service to require user validation
• Implement network-level access controls to restrict SSE service access to trusted IP ranges only
• Consider disabling or removing the SSE service if it is not essential to operations until a patch is available
• Use application-layer firewalls (WAF) to filter and validate SSE connection requests

# Example: Restrict access to SSE service via iptables
# Allow only trusted IP ranges to access SSE service port
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -s 192.168.0.0/16 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP