Fix SSRF in TypeScript and Next.js
==================================

Attach the policy to the connection, not the hostname string. Allow only
http/https and ports 80/443, reject credentials; resolve the host (or read an
IP literal in any notation) and reject loopback, private, link-local and
IPv4-mapped addresses; connect to the vetted IP with node:http, not fetch();
re-validate every redirect; cap time and bytes.

Page: https://softwaresecurity.com/fix/ssrf/typescript-nextjs/

What is in this archive
-----------------------
ssrf/typescript-nextjs/   the project: three implementations of the same code and one test suite
  lib/impl/vulnerable.ts   (vulnerable)
  lib/impl/fixed.ts   (fixed)
  lib/impl/wrong.ts   (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 (route handlers use the default Node.js runtime;
  node:http, node:net and node:dns are not available on the Edge runtime);
  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 ssrf/typescript-nextjs 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
    IMPL=fixed npm test --silent
    # an exploit test fails
    IMPL=vulnerable npm test --silent
    # a test fails
    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 ssrf/typescript-nextjs
    node run-all.mjs ssrf/typescript-nextjs

Verified
--------
  11 October 2026 on macOS 27.0 (Darwin 27.0.0, arm64), with node 26.11.1, npm
  11.20.0, next 16.4.0, react 19.3.0, vitest 5.0.3 (Vite 8.3.4), typescript
  6.0.3, semgrep 1.180.0. 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.
