As noted in the article (https://httproxy.org/), Net::HTTP and URI::Generic.find_proxy has mitigation about this vulnerability.
The remaining issue was that when external programs was spawned in cgi handlers could be effected by HTTP_PROXY env. Is it right?
I don't have ssh key right now, I can commit it and backport at tonight.
How about the stable package releases?
Unfortunately I'm going to be offline this weekend. I can handle the release work on the next monday's night at the fastest.