Unrestricted RPC Access in Azure NSGs

ID: azure-nsg-rpc-unrestricted

Severity: high

Author: princechaddha

Tags: cloud,devops,azure,microsoft,nsg,azure-cloud-config

Description

Ensure that Microsoft Azure network security groups (NSGs) do not allow unrestricted access on TCP port 135, used by Remote Procedure Call (RPC), to prevent unauthorized access and potential exploitation of network services.

YAML Source

id: azure-nsg-rpc-unrestricted
info:
  name: Unrestricted RPC Access in Azure NSGs
  author: princechaddha
  severity: high
  description: |
    Ensure that Microsoft Azure network security groups (NSGs) do not allow unrestricted access on TCP port 135, used by Remote Procedure Call (RPC), to prevent unauthorized access and potential exploitation of network services.
  impact: |
    Unrestricted access on TCP port 135 can expose services to remote execution attacks or unauthorized procedures calls, leading to significant security vulnerabilities.
  remediation: |
    Configure NSG rules to restrict access on TCP port 135. Ensure only necessary systems can initiate RPC, and apply strict monitoring and logging to detect unusual activities.
  reference:
    - https://docs.microsoft.com/en-us/azure/virtual-network/network-security-groups-overview
  tags: cloud,devops,azure,microsoft,nsg,azure-cloud-config

flow: |
  code(1);
  for (let NsgData of iterate(template.nsgdata)) {
    NsgData = JSON.parse(NsgData)
    set("nsg", NsgData.name)
    set("resourcegroup", NsgData.resourceGroup)
    code(2)
  }

self-contained: true
code:
  - engine:
      - sh
      - bash
    source: |
      az network nsg list --query '[*].{name:name, resourceGroup:resourceGroup}' --output json

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

  - engine:
      - sh
      - bash
    source: |
      az network nsg rule list --nsg-name $nsg --resource-group $resourcegroup --query "[?direction=='Inbound' && access=='Allow' && protocol=='TCP' && (destinationPortRange=='135')]"

    matchers:
      - type: word
        words:
          - '"sourceAddressPrefix": "*"'
          - '"sourceAddressPrefix": "internet"'
          - '"sourceAddressPrefix": "any"'

    extractors:
      - type: dsl
        dsl:
          - 'nsg + " has unrestricted access on TCP port 135"'
# digest: 4a0a00473045022100d1f8acdd182598809ad7e962914639af5eaf97e33b8a6e065cf89ba96288918502200c9a4c0506bd03a27bc0939c468d695147cd9eed438100731f436ecef8ae03ff: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/azure/network/azure-nsg-rpc-unrestricted.yaml"

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