Security group egress CIDR open to world

Docs > Datadog Security > Code Security > Infrastructure as Code (IaC) Security > IaC Security Rules > Security group egress CIDR open to world

Metadata

Id: 1cc2fbd7-816c-4fbf-ad6d-38a4afa4312a

Cloud Provider: AWS

Platform: CloudFormation

Severity: Medium

Category: Networking and Firewall

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Provider Reference

Description

Egress rules that allow 0.0.0.0/0 or ::/0 permit unrestricted outbound traffic to the internet. This can enable data exfiltration and communications with malicious command-and-control infrastructure.

In CloudFormation, check AWS::EC2::SecurityGroupEgress resources and AWS::EC2::SecurityGroup resources’ Properties.SecurityGroupEgress entries. CidrIp must not be 0.0.0.0/0 and CidrIpv6 must not be ::/0. Resources with these values set will be flagged. Restrict egress to specific destination CIDR ranges, reference other security groups, or route outbound traffic through centralized egress controls (NAT gateways, proxies, or firewalls) to meet this requirement.

Secure configuration example:

MySecurityGroup:
  Type: AWS::EC2::SecurityGroup
  Properties:
    GroupDescription: Restricted outbound access
    SecurityGroupEgress:
      - IpProtocol: tcp
        FromPort: 443
        ToPort: 443
        CidrIp: 10.0.0.0/16

Compliant Code Examples

Resources:
  InstanceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow http to client host
      VpcId:
         Ref: myVPC
      SecurityGroupIngress:
      - IpProtocol: tcp
        Description: TCP
        FromPort: 80
        ToPort: 80
        CidrIp: 192.0.2.0/24
      SecurityGroupEgress:
      - IpProtocol: tcp
        Description: TCP
        FromPort: 80
        ToPort: 80
        CidrIp: 192.0.2.0/24
  OutboundRule:
    Type: AWS::EC2::SecurityGroupEgress
    Properties:
      Description: TCP
      IpProtocol: tcp
      FromPort: 0
      ToPort: 0
      CidrIpv6: 2001:0DB8:1234::/48
      DestinationSecurityGroupId:
        Fn::GetAtt:
        - TargetSG
        - GroupId
      GroupId:
        Fn::GetAtt:
        - SourceSG
        - GroupId
  InboundRule:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: TCP
      IpProtocol: tcp
      FromPort: 0
      ToPort: 0
      CidrIpv6: 2001:0DB8:1234::/48
      SourceSecurityGroupId:
        Fn::GetAtt:
        - SourceSG
        - GroupId
      GroupId:
        Fn::GetAtt:
        - TargetSG
        - GroupId

{
  "Resources": {
    "InstanceSecurityGroup": {
      "Properties": {
        "GroupDescription": "Allow http to client host",
        "VpcId": {
          "Ref": "myVPC"
        },
        "SecurityGroupIngress": [
          {
            "IpProtocol": "tcp",
            "Description": "TCP",
            "FromPort": 80,
            "ToPort": 80,
            "CidrIp": "192.0.2.0/24"
          }
        ],
        "SecurityGroupEgress": [
          {
            "IpProtocol": "tcp",
            "Description": "TCP",
            "FromPort": 80,
            "ToPort": 80,
            "CidrIp": "192.0.2.0/24"
          }
        ]
      },
      "Type": "AWS::EC2::SecurityGroup"
    },
    "OutboundRule": {
      "Type": "AWS::EC2::SecurityGroupEgress",
      "Properties": {
        "Description": "TCP",
        "IpProtocol": "tcp",
        "FromPort": 0,
        "ToPort": 0,
        "CidrIpv6": "2001:0DB8:1234::/48",
        "DestinationSecurityGroupId": {
          "Fn::GetAtt": [
            "TargetSG",
            "GroupId"
          ]
        },
        "GroupId": {
          "Fn::GetAtt": [
            "SourceSG",
            "GroupId"
          ]
        }
      }
    },
    "InboundRule": {
      "Type": "AWS::EC2::SecurityGroupIngress",
      "Properties": {
        "Description": "TCP",
        "IpProtocol": "tcp",
        "FromPort": 0,
        "ToPort": 0,
        "CidrIpv6": "2001:0DB8:1234::/48",
        "SourceSecurityGroupId": {
          "Fn::GetAtt": [
            "SourceSG",
            "GroupId"
          ]
        },
        "GroupId": {
          "Fn::GetAtt": [
            "TargetSG",
            "GroupId"
          ]
        }
      }
    }
  }
}

Non-Compliant Code Examples

{
  "Resources": {
    "InstanceSecurityGroup": {
      "Type": "AWS::EC2::SecurityGroup",
      "Properties": {
        "SecurityGroupIngress": [
          {
            "IpProtocol": "tcp",
            "Description": "TCP",
            "FromPort": 80,
            "ToPort": 80,
            "CidrIp": "0.0.0.0/0"
          }
        ],
        "SecurityGroupEgress": [
          {
            "CidrIp": "0.0.0.0/0",
            "IpProtocol": "tcp",
            "Description": "TCP",
            "FromPort": 80,
            "ToPort": 80
          }
        ],
        "GroupDescription": "Allow http to client host",
        "VpcId": {
          "Ref": "myVPC"
        }
      }
    },
    "OutboundRule": {
      "Properties": {
        "FromPort": 0,
        "ToPort": 65535,
        "CidrIpv6": "::/0",
        "DestinationSecurityGroupId": {
          "Fn::GetAtt": [
            "TargetSG",
            "GroupId"
          ]
        },
        "GroupId": {
          "Fn::GetAtt": [
            "SourceSG",
            "GroupId"
          ]
        },
        "Description": "TCP",
        "IpProtocol": "tcp"
      },
      "Type": "AWS::EC2::SecurityGroupEgress"
    },
    "InboundRule": {
      "Type": "AWS::EC2::SecurityGroupIngress",
      "Properties": {
        "GroupId": {
          "Fn::GetAtt": [
            "TargetSG",
            "GroupId"
          ]
        },
        "Description": "TCP",
        "IpProtocol": "tcp",
        "FromPort": 0,
        "ToPort": 65535,
        "CidrIpv6": "::/0",
        "SourceSecurityGroupId": {
          "Fn::GetAtt": [
            "SourceSG",
            "GroupId"
          ]
        }
      }
    }
  }
}

Resources:
  InstanceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow http to client host
      VpcId:
         Ref: myVPC
      SecurityGroupIngress:
      - IpProtocol: tcp
        Description: TCP
        FromPort: 80
        ToPort: 80
        CidrIp: 0.0.0.0/0
      SecurityGroupEgress:
      - IpProtocol: tcp
        Description: TCP
        FromPort: 80
        ToPort: 80
        CidrIp: 0.0.0.0/0
  OutboundRule:
    Type: AWS::EC2::SecurityGroupEgress
    Properties:
      Description: TCP
      IpProtocol: tcp
      FromPort: 0
      ToPort: 65535
      CidrIpv6: ::/0
      DestinationSecurityGroupId:
        Fn::GetAtt:
        - TargetSG
        - GroupId
      GroupId:
        Fn::GetAtt:
        - SourceSG
        - GroupId
  InboundRule:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: TCP
      IpProtocol: tcp
      FromPort: 0
      ToPort: 65535
      CidrIpv6: ::/0
      SourceSecurityGroupId:
        Fn::GetAtt:
        - SourceSG
        - GroupId
      GroupId:
        Fn::GetAtt:
        - TargetSG
        - GroupId