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PCI DSS 4.0 Remediation 2025: 21 Battle-Tested Fixes

#security #devsecops #webdev #cybersecurity

As of 2025, the future-dated PCI DSS v4.0 controls are now assessed in your RoC/SAQ. If you’re an engineer owning auth, checkout, or infra around the CDE, here’s a fast, developer-first remediation checklist packed with real code and evidence patterns that stick in audits.

What changed & why devs should care (quick recap)

  • Controls are now “in place” in 2025 assessments; your changes and proofs must be production-ready.
  • Developer-owned surfaces (auth, payments, logging, build pipelines, external scripts) are now a critical audit path.
  • Evidence quality matters. Link code, tests, and screenshots directly to control IDs to avoid rework at QSA time.

PCI DSS 4.0 Remediation 2025: 21 Battle-Tested Fixes

Need a pre-assessment sweep to catch obvious exposures? Run an external exposure check with our free scanner before you start the sprint.

The Cheatsheet — 21 fixes you can ship this week

A) MFA for all CDE access (interactive + non-interactive)

1) Enforce MFA claims in app middleware (Express/Node):

// cde-mfa-guard.js
module.exports = function cdeMfaGuard(req, res, next) {
  // Require second factor for any route under /cde
  const mfaOk = req.user?.second_factor_verified === true;
  if (!mfaOk) return res.status(401).json({ error: "MFA required" });
  next();
};

// usage
const cdeMfaGuard = require("./cde-mfa-guard");
app.use("/cde", cdeMfaGuard);
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2) Enforce MFA for SSH (TOTP)

# /etc/ssh/sshd_config
KbdInteractiveAuthentication yes
AuthenticationMethods publickey,keyboard-interactive
# then configure Google Authenticator / PAM OTP
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3) Short-lived admin sessions with step-up MFA

// Step-up on sensitive actions
if (!req.user.mfa_recent || Date.now() - req.user.mfa_recent > 5*60*1000) {
  return res.status(403).json({ step_up_required: true });
}
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B) Strong authentication defaults

4) Argon2 or scrypt for password hashing (Node):

const argon2 = require("argon2");
const hash = await argon2.hash(plain, { type: argon2.argon2id, timeCost:3, memoryCost: 2**16, parallelism:1 });
const ok = await argon2.verify(hash, candidate);
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5) Laravel password rules + lockout

// app/Http/Controllers/Auth/RegisterController.php
$request->validate([
  'password' => ['required','string','min:12','regex:/[A-Z]/','regex:/[a-z]/','regex:/[0-9]/','regex:/[^A-Za-z0-9]/']
]);

// Throttle logins (app/Http/Kernel.php)
'throttle:5,1' // 5 attempts per minute
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6) Django: Argon2 + re-auth

# settings.py
PASSWORD_HASHERS = ["django.contrib.auth.hashers.Argon2PasswordHasher"]

# views.py - step-up reauthentication for checkout confirm
if not request.session.get("reauth_ts") or time.time()-request.session["reauth_ts"]>300:
    return redirect("reauth")
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C) Payment-page script integrity & tamper detection

7) Subresource Integrity (SRI)

<script src="/static/js/checkout.js"
        integrity="sha384-Base64HASH"
        crossorigin="anonymous"></script>
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8) Strict CSP w/ nonces (Nginx)

add_header Content-Security-Policy "default-src 'none'; base-uri 'self';
  script-src 'self' 'nonce-{RANDOM}' 'strict-dynamic';
  connect-src 'self' https://api.yourpsp.example;
  style-src 'self';
  img-src 'self' data:;
  frame-ancestors 'none';
  require-trusted-types-for 'script'" always;
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9) Detect unexpected scripts (MutationObserver)

const allowedHashes = new Set(["sha384-...","sha384-..."]);
const report = (m) => fetch("/csp/report", {method:"POST",body:JSON.stringify(m)});
new MutationObserver(muts=>{
  for (const m of muts) {
    m.addedNodes.forEach(n=>{
      if (n.tagName === "SCRIPT") {
        const sri = n.getAttribute("integrity");
        if (!sri || !allowedHashes.has(sri)) report({type:"script_added", src:n.src||"inline"});
      }
    });
  }
}).observe(document.documentElement,{childList:true,subtree:true});
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10) Generate SRI hashes (OpenSSL)

openssl dgst -sha384 -binary public/checkout.js | openssl base64 -A
# prepend "sha384-" to the output and place into integrity=""
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D) Centralized logging with alerting (developer-controlled)

11) JSON audit logs (Node + Winston → Syslog)

const { createLogger, transports, format } = require("winston");
const Syslog = require("winston-syslog").Syslog;
const log = createLogger({
  level: "info",
  format: format.json(),
  transports: [ new Syslog({ host: "10.0.0.10", port: 514, protocol: "udp4" }) ]
});
log.info({evt:"login", user:req.user.id, mfa:req.user.mfa, ip:req.ip});
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12) Python → remote syslog

import logging, logging.handlers, json
h = logging.handlers.SysLogHandler(address=("10.0.0.10",514))
log = logging.getLogger("audit"); log.setLevel(logging.INFO); log.addHandler(h)
log.info(json.dumps({"evt":"checkout_start","order":order_id,"user":uid}))
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13) rsyslog forwarder

# /etc/rsyslog.d/50-forward.conf
*.* @10.0.0.10:514;RSYSLOG_SyslogProtocol23Format
systemctl restart rsyslog
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14) Alert on auth anomalies (pseudo-rule)

# alert: many_failed_logins.yaml
when: every 5m
match: event.evt == "login_failed" | group_by(ip) | count >= 10
then: notify("pagerduty", summary: "Brute-force suspected from ${ip}")
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E) Quarterly ASV scans & pre-scan exposure sweeps

15) Cron helper to pre-check headers & redirects

# /usr/local/bin/pre_asv_sweep.sh
set -e
DOMAINS=("shop.example.com" "cdn.example.com" "pay.example.com")
for d in "${DOMAINS[@]}"; do
  echo "== $d =="
  curl -sI "https://$d" | egrep -i 'strict-transport-security|content-security-policy|x-frame-options|location'
done
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# Run monthly; ASV remains quarterly by policy
0 3 1 * * /usr/local/bin/pre_asv_sweep.sh | mail -s "Pre-ASV sweep" secops@example.com
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16) Stage-only scanning allowlist (nginx)

# block scanners on prod except approved
geo $scanner { default 0; 203.0.113.50 1; } # ASV IP example
if ($scanner = 0) { return 403; }
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For a quick external exposure sweep before booking the official ASV, use the free security scanner to catch missing headers and obvious exposures.

F) Protect the pipeline (build & deploy hardening)

17) Pin dependencies with signature checking

# npm
npm config set audit-level high
npm ci --omit=dev
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# GitHub Actions
- uses: sigstore/cosign-installer@v3
- run: cosign verify --key cosign.pub ghcr.io/org/checkout-api@${{ github.sha }}
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18) Secrets: one-time, just-in-time

# ephemeral tokens on deploy
- name: Mint short-lived token
  run: gh auth token --scopes "contents:read,packages:read" --ttl 10m > $GITHUB_OUTPUT
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G) Network & store configurations

19) TLS everywhere (HSTS + OCSP must-staple)

add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
ssl_stapling on; ssl_stapling_verify on;
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20) Least privilege DB access (read/write split)

CREATE USER checkout_writer WITH PASSWORD '...';
GRANT INSERT, UPDATE ON orders, payments TO checkout_writer;
REVOKE SELECT ON cardholder_data FROM checkout_writer; -- never needed
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21) Tokenize; never store PAN

// receive tokenized instrument from PSP; never touch PAN
app.post("/pay", async (req,res) => {
  const { token, amount } = req.body; // token from PSP JS
  // server-side confirmation using PSP SDK/APIs
});
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“Evidence that sticks” (copy-paste templates)

Pull Request template (map work → control IDs):

### Control IDs
- 8.3.1 MFA for all access to CDE: [ ] Yes  [ ] N/A
- 6.4.3 Change control with approvals: [ ] Yes
- 10.x Logging of payment events: [ ] Yes

### Evidence
- Code: `app/middleware/cde-mfa-guard.js`
- Config: `nginx/csp.conf` (screenshot in artifacts)
- Tests: `tests/csp_header.spec.ts` (attached report)
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Header test (Express + supertest):

it("sets strict CSP on /checkout", async () => {
  const res = await request(app).get("/checkout");
  expect(res.headers["content-security-policy"]).toMatch(/script-src .*'strict-dynamic'/);
});
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Config snapshot script (immutable proofs):

tar czf evidence-$(date +%F).tar.gz nginx/*.conf app/*.json terraform/*.tf
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Run a quick exposure sweep before your QSA

  • Step 1: Open our Free Website Vulnerability Scanner.
  • Step 2: Test all public hostnames involved in checkout (storefront, CDN, payment subdomains).
  • Step 3: Fix missing headers/redirects, re-run until clean.

Screenshot: Free Website Vulnerability Scanner Tool

Screenshot of the free tools webpage where you can access security assessment tools.Screenshot of the free tools webpage where you can access security assessment tools.

Sample vulnerability report to check Website Vulnerability

Sample vulnerability assessment report generated with our free tool, providing insights into possible vulnerabilities.Sample vulnerability assessment report generated with our free tool, providing insights into possible vulnerabilities.

Where we can help (links for dev leads & managers)

Related reading from our blog (good for dev handoffs)

Final CTA

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