diff --git a/lib/importmap/commands.rb b/lib/importmap/commands.rb
index ea5025d..73e97ea 100644
--- a/lib/importmap/commands.rb
+++ b/lib/importmap/commands.rb
@@ -1,5 +1,6 @@
 require "thor"
 require "importmap/packager"
+require "importmap/npm"
 
 class Importmap::Commands < Thor
   include Thor::Actions
@@ -63,11 +64,54 @@ def json
     puts Rails.application.importmap.to_json(resolver: ActionController::Base.helpers)
   end
 
+  desc "audit", "Run a security audit"
+  def audit
+    vulnerable_packages = npm.vulnerable_packages
+
+    if vulnerable_packages.any?
+      table = [["Package", "Severity", "Vulnerable versions", "Vulnerability"]]
+      vulnerable_packages.each { |p| table << [p.name, p.severity, p.vulnerable_versions, p.vulnerability] }
+
+      puts_table(table)
+      vulnerabilities = 'vulnerability'.pluralize(vulnerable_packages.size)
+      severities = vulnerable_packages.map(&:severity).tally.sort_by(&:last).reverse
+                                      .map { |severity, count| "#{count} #{severity}" }
+                                      .join(", ")
+      puts "  #{vulnerable_packages.size} #{vulnerabilities} found: #{severities}"
+
+      exit 1
+    else
+      puts "No vulnerable packages found"
+    end
+  end
+
+  desc "outdated", "Check for outdated packages"
+  def outdated
+    outdated_packages = npm.outdated_packages
+
+    if outdated_packages.any?
+      table = [["Package", "Current", "Latest"]]
+      outdated_packages.each { |p| table << [p.name, p.current_version, p.latest_version || p.error] }
+
+      puts_table(table)
+      packages = 'package'.pluralize(outdated_packages.size)
+      puts "  #{outdated_packages.size} outdated #{packages} found"
+
+      exit 1
+    else
+      puts "No outdated packages found"
+    end
+  end
+
   private
     def packager
       @packager ||= Importmap::Packager.new
     end
 
+    def npm
+      @npm ||= Importmap::Npm.new
+    end
+
     def remove_line_from_file(path, pattern)
       path = File.expand_path(path, destination_root)
 
@@ -78,6 +122,21 @@ def remove_line_from_file(path, pattern)
         with_lines_removed.each { |line| file.write(line) }
       end
     end
+
+    def puts_table(array)
+      column_sizes = array.reduce([]) do |lengths, row|
+        row.each_with_index.map{ |iterand, index| [lengths[index] || 0, iterand.to_s.length].max }
+      end
+
+      puts head = "+" + (column_sizes.map { |s| "-" * (s + 2) }.join('+')) + '+'
+      array.each_with_index do |row, row_number|
+        row = row.fill(nil, row.size..(column_sizes.size - 1))
+        row = row.each_with_index.map { |v, i| v.to_s + " " * (column_sizes[i] - v.to_s.length) }
+        puts "| " + row.join(" | ") + " |"
+        puts head if row_number == 0
+      end
+      puts head
+    end
 end
 
 Importmap::Commands.start(ARGV)
diff --git a/lib/importmap/npm.rb b/lib/importmap/npm.rb
new file mode 100644
index 0000000..a24bba5
--- /dev/null
+++ b/lib/importmap/npm.rb
@@ -0,0 +1,113 @@
+require "net/http"
+require "uri"
+require "json"
+
+class Importmap::Npm
+  Error     = Class.new(StandardError)
+  HTTPError = Class.new(Error)
+
+  singleton_class.attr_accessor :base_uri
+  self.base_uri = URI("https://registry.npmjs.org")
+
+  def initialize(importmap_path = "config/importmap.rb")
+    @importmap_path = Pathname.new(importmap_path)
+  end
+
+  def outdated_packages
+    packages_with_versions.each.with_object([]) do |(package, current_version), outdated_packages|
+      outdated_package = OutdatedPackage.new(name: package,
+                                             current_version: current_version)
+
+      if !(response = get_package(package))
+        outdated_package.error = 'Response error'
+      elsif (error = response['error'])
+        outdated_package.error = error
+      else
+        latest_version = find_latest_version(response)
+        next unless outdated?(current_version, latest_version)
+
+        outdated_package.latest_version = latest_version
+      end
+
+      outdated_packages << outdated_package
+    end.sort_by(&:name)
+  end
+
+  def vulnerable_packages
+    get_audit.flat_map do |package, vulnerabilities|
+      vulnerabilities.map do |vulnerability|
+        VulnerablePackage.new(name: package,
+                              severity: vulnerability['severity'],
+                              vulnerable_versions: vulnerability['vulnerable_versions'],
+                              vulnerability: vulnerability['title'])
+      end
+    end.sort_by { |p| [p.name, p.severity] }
+  end
+
+  private
+    OutdatedPackage   = Struct.new(:name, :current_version, :latest_version, :error, keyword_init: true)
+    VulnerablePackage = Struct.new(:name, :severity, :vulnerable_versions, :vulnerability, keyword_init: true)
+
+    def packages_with_versions
+      # We cannot use the name after "pin" because some dependencies are loaded from inside packages
+      # Eg. pin "buffer", to: "https://ga.jspm.io/npm:@jspm/core@2.0.0-beta.19/nodelibs/browser/buffer.js"
+
+      importmap.scan(/^pin .*(?<=npm:|npm\/|skypack\.dev\/|unpkg\.com\/)(.*)(?=@\d+\.\d+\.\d+)@(\d+\.\d+\.\d+(?:[^\/\s"]*)).*$/) |
+        importmap.scan(/^pin "([^"]*)".* #.*@(\d+\.\d+\.\d+(?:[^\s]*)).*$/)
+    end
+
+    def importmap
+      @importmap ||= File.read(@importmap_path)
+    end
+
+    def get_package(package)
+      uri = self.class.base_uri.dup
+      uri.path = "/" + package
+      response = get_json(uri)
+
+      JSON.parse(response)
+    rescue JSON::ParserError
+      nil
+    end
+
+    def get_json(uri)
+      Net::HTTP.get(uri, "Content-Type" => "application/json")
+    rescue => error
+      raise HTTPError, "Unexpected transport error (#{error.class}: #{error.message})"
+    end
+
+    def find_latest_version(response)
+      latest_version = response.dig('dist-tags', 'latest')
+      return latest_version if latest_version
+
+      return unless response['versions']
+
+      response['versions'].keys.map { |v| Gem::Version.new(v) rescue nil }.compact.sort.last
+    end
+
+    def outdated?(current_version, latest_version)
+      Gem::Version.new(current_version) < Gem::Version.new(latest_version)
+    rescue ArgumentError
+      current_version.to_s < latest_version.to_s
+    end
+
+    def get_audit
+      uri = self.class.base_uri.dup
+      uri.path = "/-/npm/v1/security/advisories/bulk"
+
+      body = packages_with_versions.each.with_object({}) { |(package, version), data|
+        data[package] ||= []
+        data[package] << version
+      }
+      return {} if body.empty?
+
+      response = post_json(uri, body)
+      JSON.parse(response.body)
+    end
+
+    def post_json(uri, body)
+      Net::HTTP.post(uri, body.to_json, "Content-Type" => "application/json")
+    rescue => error
+      raise HTTPError, "Unexpected transport error (#{error.class}: #{error.message})"
+    end
+end
diff --git a/test/fixtures/files/outdated_import_map.rb b/test/fixtures/files/outdated_import_map.rb
new file mode 100644
index 0000000..450c589
--- /dev/null
+++ b/test/fixtures/files/outdated_import_map.rb
@@ -0,0 +1 @@
+pin "md5", to: "https://cdn.skypack.dev/md5@2.2.0", preload: true
diff --git a/test/fixtures/files/vulnerable_import_map.rb b/test/fixtures/files/vulnerable_import_map.rb
new file mode 100644
index 0000000..48e61a8
--- /dev/null
+++ b/test/fixtures/files/vulnerable_import_map.rb
@@ -0,0 +1 @@
+pin "is-svg", to: "https://cdn.skypack.dev/is-svg@3.0.0", preload: true
diff --git a/test/npm_integration_test.rb b/test/npm_integration_test.rb
new file mode 100644
index 0000000..2dcbe5f
--- /dev/null
+++ b/test/npm_integration_test.rb
@@ -0,0 +1,67 @@
+require "test_helper"
+require "importmap/npm"
+
+class Importmap::NpmIntegrationTest < ActiveSupport::TestCase
+  test "successful outdated packages against live service" do
+    file = file_fixture("outdated_import_map.rb")
+    npm = Importmap::Npm.new(file)
+
+    outdated_packages = npm.outdated_packages
+
+    assert_equal(1, outdated_packages.size)
+    assert_equal("md5", outdated_packages[0].name)
+    assert_equal("2.2.0", outdated_packages[0].current_version)
+    assert_match(/\d+\.\d+\.\d+/, outdated_packages[0].latest_version)
+  end
+
+  test "failed outdated packages request against live bad domain" do
+    file = file_fixture("outdated_import_map.rb")
+    npm = Importmap::Npm.new(file)
+
+    original_base_uri = Importmap::Npm.base_uri
+    Importmap::Npm.base_uri = URI("https://invalid.error")
+
+    assert_raises(Importmap::Npm::HTTPError) do
+      npm.outdated_packages
+    end
+  ensure
+    Importmap::Npm.base_uri = original_base_uri
+  end
+
+  test "successful vulnerable packages against live service" do
+    file = file_fixture("vulnerable_import_map.rb")
+    npm = Importmap::Npm.new(file)
+
+    vulnerable_packages = npm.vulnerable_packages
+
+    assert(vulnerable_packages.size >= 2)
+
+    assert_equal("is-svg", vulnerable_packages[0].name)
+    assert_equal("is-svg", vulnerable_packages[1].name)
+
+    severities = vulnerable_packages.map(&:severity)
+    assert_includes(severities, "high")
+
+    vulnerabilities = vulnerable_packages.map(&:vulnerability)
+    assert_includes(vulnerabilities, "ReDOS in IS-SVG")
+    assert_includes(vulnerabilities, "Regular Expression Denial of Service (ReDoS)")
+
+    vulnerable_versions = vulnerable_packages.map(&:vulnerable_versions)
+    assert_includes(vulnerable_versions, ">=2.1.0 <4.3.0")
+    assert_includes(vulnerable_versions, ">=2.1.0 <4.2.2")
+  end
+
+  test "failed vulnerable packages request against live bad domain" do
+    file = file_fixture("vulnerable_import_map.rb")
+    npm = Importmap::Npm.new(file)
+
+    original_base_uri = Importmap::Npm.base_uri
+    Importmap::Npm.base_uri = URI("https://invalid.error")
+
+    assert_raises(Importmap::Npm::HTTPError) do
+      npm.vulnerable_packages
+    end
+  ensure
+    Importmap::Npm.base_uri = original_base_uri
+  end
+end
diff --git a/test/npm_test.rb b/test/npm_test.rb
new file mode 100644
index 0000000..a60c636
--- /dev/null
+++ b/test/npm_test.rb
@@ -0,0 +1,69 @@
+require "test_helper"
+require "importmap/npm"
+require "minitest/mock"
+
+class Importmap::NpmTest < ActiveSupport::TestCase
+  setup { @npm = Importmap::Npm.new(file_fixture("outdated_import_map.rb")) }
+
+  test "successful outdated packages with mock" do
+    response = { "dist-tags" => { "latest" => '2.3.0' } }.to_json
+
+    @npm.stub(:get_json, response) do
+      outdated_packages = @npm.outdated_packages
+
+      assert_equal(1, outdated_packages.size)
+      assert_equal('md5', outdated_packages[0].name)
+      assert_equal('2.2.0', outdated_packages[0].current_version)
+      assert_equal('2.3.0', outdated_packages[0].latest_version)
+    end
+  end
+
+  test "missing outdated packages with mock" do
+    response = { "error" => "Not found" }.to_json
+
+    @npm.stub(:get_json, response) do
+      outdated_packages = @npm.outdated_packages
+
+      assert_equal(1, outdated_packages.size)
+      assert_equal('md5', outdated_packages[0].name)
+      assert_equal('2.2.0', outdated_packages[0].current_version)
+      assert_equal('Not found', outdated_packages[0].error)
+    end
+  end
+
+  test "failed outdated packages request with mock" do
+    Net::HTTP.stub(:get, proc { raise "Unexpected Error" }) do
+      assert_raises(Importmap::Npm::HTTPError) do
+        @npm.outdated_packages
+      end
+    end
+  end
+
+  test "successful vulnerable packages with mock" do
+    response = Class.new do
+      def body
+        { "md5" => [{ "title" => "Unsafe hashing", "severity" => "high", "vulnerable_versions" => "<42.0.0" }] }.to_json
+      end
+
+      def code() "200" end
+    end.new
+
+    @npm.stub(:post_json, response) do
+      vulnerable_packages = @npm.vulnerable_packages
+
+      assert_equal(1, vulnerable_packages.size)
+      assert_equal('md5', vulnerable_packages[0].name)
+      assert_equal('Unsafe hashing', vulnerable_packages[0].vulnerability)
+      assert_equal('high', vulnerable_packages[0].severity)
+      assert_equal('<42.0.0', vulnerable_packages[0].vulnerable_versions)
+    end
+  end
+
+  test "failed vulnerable packages request with mock" do
+    Net::HTTP.stub(:post, proc { raise "Unexpected Error" }) do
+      assert_raises(Importmap::Npm::HTTPError) do
+        @npm.vulnerable_packages
+      end
+    end
+  end
+end