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Application Load Balancer should be configured to drop invalid http headers

Ensure that your Elastic Load Balancers (ELB) are configured to drop invalid http header.

How to fix

Attribute drop_invalid_header_fields of aws_lb must be true.

Implementation options

Choose the option that matches how you manage Terraform. All options satisfy this control.

Use the compliance.tf registry module to get this control enforced by default. This control is mapped to the frameworks shown in the tabs above. To begin, see get started with compliance.tf.

module "alb" {
  source  = "fedramplow.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "gdpr.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "hipaa.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "hipaasecurity2003.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "nist800171.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "nist80053rev4.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "nistcsfv11.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "nydfs23.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "pcidssv321.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "rbicybersecurity.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "rbiitfnbfc.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

module "alb" {
  source  = "soc2.compliance.tf/terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"
}

Option 2: Open source module (terraform-aws-modules)

If you use terraform-aws-modules/alb/aws, configure the required module inputs to satisfy this control. You can later migrate to the compliance.tf module with minimal changes because it is compatible by design.

module "alb" {
  source  = "terraform-aws-modules/alb/aws"
  version = ">=10.0.0,<11.0.0"

  access_logs = {
    bucket = "example-bucket-abc123"
  }
  load_balancer_type = "application"
  name               = "abc123"
  security_groups    = ["sg-abc12345"]
  subnets            = ["subnet-abc123", "subnet-def456"]
  target_groups = {
    default = {
      create_attachment = false
      name_prefix       = "def-"
      port              = 443
      protocol          = "HTTPS"
      target_type       = "ip"
    }
  }
  vpc_id = "vpc-12345678"

  drop_invalid_header_fields = true
}

Option 3: Terraform AWS provider resources

If you manage resources directly, configure the relevant Terraform AWS provider resources to meet this control. See docs for the resources involved: aws_lb.

resource "aws_lb" "this" {
  access_logs {
    bucket = "pofix-example-lb-logs"
  }
  internal = true
  name     = "pofix-example-lb"
  subnets  = ["subnet-abc123", "subnet-def456"]

  drop_invalid_header_fields = true
}
Which option should I choose?
  • Compliance.tf module (recommended): controls enforced by default and mapped to frameworks.
  • Open source module (terraform-aws-modules): compatible by design with compliance.tf. Same variable names for an easy, low-change migration path when you are ready.
  • Terraform AWS provider resources: manage Terraform resources directly.

Tool mappings

Use these identifiers to cross-reference this control across tools, reports, and evidence.

  • Compliance.tf (CTF) Control: elb_application_lb_http_drop_invalid_header_enabled

  • AWS Config Managed Rule: ALB_HTTP_DROP_INVALID_HEADER_ENABLED

  • Checkov Check: CKV_AWS_131

  • Powerpipe Controls: aws_compliance.control.elb_application_lb_drop_http_headers, aws_compliance.control.elb_application_lb_http_drop_invalid_header_enabled