Netty project is an event-driven asynchronous network application framework. Starting in version 4.1.83.Final and prior to 4.1.86.Final, when calling DefaultHttpHeadesr.set with an _iterator_ of values, header value validation was not performed, allowing malicious header values in the iterator to perform HTTP Response Splitting. This issue has been patched in version 4.1.86.Final.

Integrators can work around the issue by changing the DefaultHttpHeaders.set(CharSequence, Iterator<?>) call, into a remove() call, and call add() in a loop over the iterator of values.