Unrestricted NACL Outbound Traffic

ID: nacl-outbound-restrict

Severity: medium

Author: princechaddha

Tags: cloud,devops,aws,amazon,vpc,aws-cloud-config

Description

Checks for Amazon VPC NACLs allowing outbound traffic to all ports, recommending restriction to necessary ports only.

YAML Source

id: nacl-outbound-restrict
info:
  name: Unrestricted NACL Outbound Traffic
  author: princechaddha
  severity: medium
  description: |
    Checks for Amazon VPC NACLs allowing outbound traffic to all ports, recommending restriction to necessary ports only.
  impact: |
    Potential for data exfiltration or unauthorized access if outbound traffic is not properly restricted.
  remediation: |
    Modify NACL outbound rules to limit traffic to only the ports required for legitimate business needs.
  reference:
    - https://docs.aws.amazon.com/vpc/latest/userguide/vpc-network-acls.html
  metadata:
    max-request: 2
  tags: cloud,devops,aws,amazon,vpc,aws-cloud-config
variables:
  region: "us-east-1"

flow: |
  code(1)
  for(let NACLIDs of iterate(template.nacls)){
    set("naclid", NACLIDs)
    code(2)
  }

self-contained: true
code:
  - engine:
      - sh
      - bash
    source: |
      aws ec2 describe-network-acls --region $region --query 'NetworkAcls[*].NetworkAclId' --output json

    extractors:
      - type: json
        name: nacls
        internal: true
        json:
          - '.[]'

  - engine:
      - sh
      - bash
    source: |
         aws ec2 describe-network-acls --region $region --network-acl-ids $naclid --query 'NetworkAcls[*].Entries[?(RuleAction==`allow`) && (Egress==`true`)] | []'

    matchers-condition: and
    matchers:
      - type: word
        words:
          - "allow"
        condition: and

      - type: word
        words:
          - "PortRange"
        negative: true

    extractors:
      - type: dsl
        dsl:
          - '"Access to the VPC subnets associated with your NACL " + naclid + " is not restricted."'
# digest: 4b0a00483046022100ce482b003459f45bc6149998a48727c1dd29cf9783b3f357d98d64f04feb0440022100fe8cced5276dcc12d9a34f7b07db1adcd9a17398b40c7eba359ea07905738165:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

$ nuclei -u "URL" -t "cloud/aws/vpc/nacl-outbound-restrict.yaml"

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