CVV / CVC / Security Code Regex for Go

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching cvv / cvc / security code, ported and verified for Go. 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 Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

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

package validation

import "regexp"

var cvvCvcSecurityCodeRe = regexp.MustCompile(`^[0-9]{3,4}$`)

func ValidateCvvCvcSecurityCode(s string) bool {
    return cvvCvcSecurityCodeRe.MatchString(s)
}

// Example
// fmt.Println(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 Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. 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.