Rack ReDoS Vulnerability in HTTP Accept Headers Parsing

Summary

A Regular Expression Denial of Service (ReDoS) vulnerability exists
in the Rack::Request::Helpers module when parsing HTTP Accept headers.
This vulnerability can be exploited by an attacker sending specially
crafted Accept-Encoding or Accept-Language headers, causing the
server to spend excessive time processing the request and leading
to a Denial of Service (DoS).

Details

The fix for https://github.com/rack/rack/security/advisories/GHSA-54rr-7fvw-6x8f
was not applied to the main branch and thus while the issue was fixed
for the Rack v3.0 release series, it was not fixed in the v3.1
release series until v3.1.5.