Open Inbound NACL Traffic

ID: nacl-open-inbound

Severity: medium

Author: princechaddha

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

Description

Checks for Amazon VPC Network ACLs with inbound rules allowing traffic from all IPs across all ports, increasing the risk of unauthorized access.

YAML Source

id: nacl-open-inbound
info:
  name: Open Inbound NACL Traffic
  author: princechaddha
  severity: medium
  description: |
    Checks for Amazon VPC Network ACLs with inbound rules allowing traffic from all IPs across all ports, increasing the risk of unauthorized access.
  impact: |
    Allows unrestricted access to resources within the subnet, potentially exposing sensitive data or services to unauthorized users.
  remediation: |
    Restrict Network ACL inbound rules to only allow necessary IP ranges and ports as per the Principle of Least Privilege.
  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==`false`)] | []'

    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: 4a0a00473045022038258a9ed742e00db36fcc2c517562a509834fddfd0ff2f229c0de8ce3d93038022100f1b4b3278f9e9987c7aa831106f107e16c7053eff871cc90f2cd512eda8671d1:922c64590222798bb761d5b6d8e72950

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-open-inbound.yaml"

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