CVV / CVC / Security Code Regex for JavaScript

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching cvv / cvc / security code, ported and verified for JavaScript. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// CVV / CVC / Security Code
// ReDoS-safe | RegexVault — Finance > Card Numbers

const cvvCvcSecurityCodeRegex = /^[0-9]{3,4}$/;

function validateCvvCvcSecurityCode(input: string): boolean {
  return cvvCvcSecurityCodeRegex.test(input);
}

// Example
console.log(validateCvvCvcSecurityCode("123")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Card Numbers category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

CVV (Visa), CVC (Mastercard), CID (Amex) are 3 digits on the back for Visa/MC/Discover, 4 digits on the front for Amex. PCI-DSS prohibits storing CVV/CVC post-authorization — never persist this value.