Fix ReDoS in Java and Spring Boot
=================================

On JDK 9+ java.util.regex memoizes to defuse many catastrophic patterns - but
a backreference turns that off, so a nested quantifier backtracks
exponentially again, and the engine has no timeout. Rewrite the pattern to
drop the nesting and the backreference so matching is linear, cap the input
length, and bound any untrusted match on an interruptible thread.

Page: https://softwaresecurity.com/fix/regex-dos/java-spring/

What is in this archive
-----------------------
regex-dos/java-spring/   the project: three implementations of the same code and one test suite
  src/main/java/com/example/redos/impl/VulnerableEmailValidator.java   (vulnerable)
  src/main/java/com/example/redos/impl/FixedEmailValidator.java   (fixed)
  src/main/java/com/example/redos/impl/WrongEmailValidator.java   (a plausible fix that still fails)
run-all.mjs   runs the tests in all three modes and checks the results (Node.js only)
LICENSE-CODE.txt

Run it
------
  Tested with OpenJDK 21.0.12.1 (Homebrew), Maven 3.9.16. run-all.mjs needs
  Node.js 22 or later. Supported versions:
  https://softwaresecurity.com/fix/versions/

  From the regex-dos/java-spring folder, install the dependencies once (this
  needs network access):

    mvn -B -q test

  Then run the tests. IMPL chooses the implementation the tests load:

    # every test passes
    IMPL=fixed mvn -B -o -q test
    # an exploit test fails
    IMPL=vulnerable mvn -B -o -q test
    # a test fails
    IMPL=wrong mvn -B -o -q test

  The JUnit report is written to target/surefire-reports/TEST-*.xml. To run all
  three modes and check the results in one step, run the harness from this top
  folder (it needs only Node.js; --install runs the install step first):

    node run-all.mjs --install regex-dos/java-spring
    node run-all.mjs regex-dos/java-spring

Verified
--------
  11 October 2026, with jdk OpenJDK 21.0.12.1, maven 3.9.16, springBoot 4.1.1,
  junitJupiter 6.0.3, os macOS 27.0, Apple M5 Max. Versions and results hold for
  that date: run the tests with your own versions before relying on the fix.

Licence
-------
  The code is MIT licensed (LICENSE-CODE.txt). The page text is CC BY 4.0.
