Fix code injection in Node.js and Express
=========================================

Do not turn a request string into code. eval, new Function and node:vm all run
it, and node:vm is not a sandbox. Parse the formula with a fixed grammar
(numbers, the allowlisted field names and the arithmetic operators) and
evaluate that over the row, so there is no function, property or global to
reach.

Page: https://softwaresecurity.com/fix/code-injection/node-express/

What is in this archive
-----------------------
code-injection/node-express/   the project: three implementations of the same code and one test suite
  impl/vulnerable.js   (vulnerable)
  impl/fixed.js   (fixed)
  impl/wrong.js   (a plausible fix that still fails)
run-all.mjs   runs the tests in all three modes and checks the results (Node.js only)
LICENSE-CODE.txt

Run it
------
  Tested with Node.js 26.11.1 (node:vm built in); package.json allows Node.js
  ^22.23.2 || ^24.18.1 || >=26.5.1. run-all.mjs needs Node.js 22 or later.
  Supported versions: https://softwaresecurity.com/fix/versions/

  From the code-injection/node-express folder, install the dependencies once
  (this needs network access):

    npm ci

  Then run the tests. IMPL chooses the implementation the tests load:

    # every test passes
    FIXCARD_SECRET=730199138246 IMPL=fixed npm test --silent
    # an exploit test fails
    FIXCARD_SECRET=730199138246 IMPL=vulnerable npm test --silent
    # a test fails
    FIXCARD_SECRET=730199138246 IMPL=wrong npm test --silent

  The JUnit report is written to reports/junit.xml. To run all three modes and
  check the results in one step, run the harness from this top folder (it needs
  only Node.js; --install runs the install step first):

    node run-all.mjs --install code-injection/node-express
    node run-all.mjs code-injection/node-express

Verified
--------
  11 October 2026 on macOS 27.0 (Darwin 27.0.0, arm64), with node 26.11.1, npm
  11.20.0. Versions and results hold for that date: run the tests with your own
  versions before relying on the fix.

Licence
-------
  The code is MIT licensed (LICENSE-CODE.txt). The page text is CC BY 4.0.
