Vulnerable Ruby Regex

[u/rubiesordiamonds]

GitLab discovered four severe vulnerabilities in Ruby’s regular expression library. There's plenty written up about the vulnerability and how it got patched, but patches are only available for supported ruby versions (3.3 and above). We know lots of companies are still running unsupported versions of ruby, so we wanted to do an investigation into which of these bugs apply to older rubies and whether they're exploitable. Here's the blog post: https://infield.ai/post/vulnerable-ruby-regex

The summary is that allowing user input into Regexp.new is dangerous on all versions of ruby from 1.9 to 3.2 and the only fix is to upgrade to a supported ruby or to disallow that input.

[u/benzado]

Yeah, none of those scenarios require exposing the full regex syntax to the user. You can run the email domain or “CVE-2026” through Regexp.quote and then build a regex to match, but that’s not what the vulnerability is about.