X.509 Certificate Serial Number Regex for Go

What this pattern does

This page provides a well-structured, multi-part regular expression for matching x.509 certificate serial number, ported and verified for Go. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. 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

// X.509 Certificate Serial Number
// ReDoS-safe | RegexVault — Security > Certificates & PKI

package validation

import "regexp"

var x509CertificateSerialNumberRe = regexp.MustCompile(`^[0-9a-f]{2}(?::[0-9a-f]{2}){7,19}$`)

func ValidateX509CertificateSerialNumber(s string) bool {
    return x509CertificateSerialNumberRe.MatchString(s)
}

// Example
// fmt.Println(ValidateX509CertificateSerialNumber("01:23:45:67:89:ab:cd:ef:01:23:45:67:89:ab:cd:ef")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > Certificates & PKI 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

X.509 serial numbers are 1-20 byte (8-160 bit) integers, typically displayed in colon-separated hex pairs. CA/Browser Forum requires serial numbers be at least 64 bits and generated with at least 64 bits of entropy. Used for certificate revocation lookups (CRL, OCSP).