HAProxy is a popular open-source software that provides high availability, load balancing, and proxying for TCP and HTTP-based applications. While it offers powerful features for managing network traffic, it is crucial to ensure that its configuration is secure to prevent unauthorized access. This blog post discusses a vulnerability where HAProxy stats are publicly accessible due to improper access control and the potential impact of this exposure.

What is the Issue?

An improperly configured HAProxy instance can expose its statistics page to the public. The stats page provides detailed information about the system's status and performance, which, if accessed by unauthorized users, can lead to sensitive information leakage by visiting this endpoint https://example.com/haproxy?stats 

Why is This a Problem?

Public access to the HAProxy stats page can lead to several security risks:

• Information Disclosure: The stats page can reveal sensitive information about the system, such as server performance, backend server details, and session data.
• Reconnaissance: Attackers can use the information obtained from the stats page to plan more targeted attacks on the infrastructure.
• Resource Monitoring: Unauthorized users can monitor system load and performance, potentially identifying windows of opportunity for launching attacks.

Impact

The impact of this vulnerability includes:

• System Info Leaks: Unauthorized access to the stats page can leak detailed system information, compromising the security and privacy of the infrastructure.
• Increased Attack Surface: Attackers can gather valuable data to exploit other vulnerabilities or weaknesses within the system.

How to Fix It

To mitigate this vulnerability, follow these best practices:

1. Restrict Access to the Stats Page: Implement access controls to ensure that only authorized users can access the HAProxy stats page. This can be done by configuring user authentication and IP whitelisting.
2. Use SSL/TLS: Ensure that the stats page is served over HTTPS to prevent data interception and man-in-the-middle attacks.
3. Regularly Review Configuration: Regularly review and update the HAProxy configuration to adhere to security best practices and address any potential vulnerabilities.

Example Configuration

To restrict access to the HAProxy stats page, you can add the following configuration to your HAProxy configuration file:

# Add this to your HAProxy configuration file

listen stats

    bind *:8404

    stats enable

    stats uri /haproxy?stats

    stats auth admin:password

    acl network_allowed src 192.168.1.0/24

    http-request allow if network_allowed

    http-request deny if !network_allowed

This configuration ensures that only users from the specified IP range (192.168.1.0/24) can access the stats page, and they must authenticate using the credentials admin:password.

Conclusion

Properly securing the HAProxy stats page is crucial to prevent unauthorized access and information leakage. By implementing strong access controls, using SSL/TLS, and regularly reviewing your configuration, you can protect your infrastructure from potential security risks. Ensuring the security of your HAProxy instance helps maintain the integrity and confidentiality of your network and its resources.

References

• HAProxy Documentation: Statistics.
• HAProxy Configuration Guide.

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