PEM Certificate Block Regex for Java

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching pem certificate block, ported and verified for Java. 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 Java project — whether you're validating in a Spring Boot controller, a Jakarta EE service, or a standalone utility class.

Java Implementation

// PEM Certificate Block
// ReDoS-safe | RegexVault — Security > Certificates & PKI

import java.util.regex.Pattern;

public class PemCertificateBlockValidator {
    private static final Pattern PATTERN =
        Pattern.compile("-----BEGIN CERTIFICATE-----[\\r\\n]+(?:[A-Za-z0-9+/=\\r\\n]{1,80}[\\r\\n]+)*-----END CERTIFICATE-----");

    public static boolean validate(String input) {
        return PATTERN.matcher(input).matches();
    }

    // Example
    public static void main(String[] args) {
        System.out.println(validate("-----BEGIN CERTIFICATE-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA
-----END CERTIFICATE-----")); // 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 Java developers because critical in Java applications since the JVM regex engine uses backtracking and is susceptible to ReDoS without careful pattern design. 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

PEM format: base64-encoded DER certificate wrapped in BEGIN/END markers. Lines are max 76 characters in the standard. Use for detecting certificates in config files, code, or traffic. Parse with a proper X.509 library to extract subject, issuer, validity, and SANs.