== How to fix it in Java SE

=== Code examples

The following noncompliant code is vulnerable to Regex Denial of Service
because untrusted data is used as a regex to scan a string without prior
sanitization or validation.

==== Noncompliant code example

[source,java,diff-id=1,diff-type=noncompliant]
----
public boolean validate(HttpServletRequest request) {
  String regex = request.getParameter("regex");
  String input = request.getParameter("input");

  return input.matches(regex);
}
----

==== Compliant solution

[source,java,diff-id=1,diff-type=compliant]
----
public boolean validate(HttpServletRequest request) {
  String regex = request.getParameter("regex");
  String input = request.getParameter("input");

  return input.matches(Pattern.quote(regex));
}
----

=== How does this work?

include::../../common/fix/validation.adoc[]

In the example, `Pattern.quote` escapes metacharacters and escape sequences that
could have broken the initially intended logic.
