ELBs With Drop Invalid Header Fields Disabled

Overview

Elastic Load Balancers (ELBs) play a crucial role in distributing incoming traffic across multiple targets to enhance application availability and reliability. However, when the option to Drop Invalid Header Fields is disabled, it exposes your infrastructure to potential security risks.

Security Concerns

1. Header Injection Attacks

• Attackers can exploit invalid headers to perform HTTP header injection, which may lead to session hijacking, cache poisoning, or security control bypasses.

2. Malformed Request Handling

• Without strict header validation, malformed requests might be processed, potentially causing application crashes or data corruption.

3. Amplified Vulnerabilities

• Allowing invalid headers increases the attack surface for vulnerabilities in downstream applications and services.

4. Compliance Issues

• Disabling this feature may violate compliance standards like PCI DSS, which require robust input validation mechanisms.

Solutions and Best Practices

1. Enable Drop Invalid Header Fields

• How to Enable:

  1. Navigate to the ELB settings in your AWS Management Console.

  2. Under Attributes, enable the option for Drop Invalid Header Fields.

  3. Save the configuration.

2. Use WAF (Web Application Firewall)

• Deploy AWS WAF in front of your ELB to filter malicious requests and block invalid headers.

3. Monitor and Log Traffic

• Enable access logging for your ELBs to monitor incoming requests.

• Use tools like Amazon CloudWatch or AWS CloudTrail to identify suspicious patterns.

4. Implement Strict Security Policies

• Use security groups and network ACLs to restrict access to trusted IP ranges and ports.

5. Regular Audits

• Conduct regular security audits to ensure compliance and identify any misconfigurations.

6. Patch Management

• Ensure all downstream applications and services are patched against known vulnerabilities that could be exploited through invalid headers.

Conclusion

Disabling the Drop Invalid Header Fields feature on ELBs introduces significant risks to your infrastructure. By enabling this feature and adopting complementary security measures, IT and Security Engineers can maintain a robust defense against potential threats.

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For further details, refer to the AWS Documentation on ELB Attributes.