The recommendation for anyone using regular expressions on hostile input is to (a) don't do that. (b) use a better regexp without this possible behavior and (c) use something like re2 (there's a Python binding at https://github.com/axiak/pyre2) which is a regular expression engine that this cannot happen to.
fixing this within python requires a complete rewrite and replacement of the re module with one that uses a different approach. see the other work on the MRAB regex module and discussion surrounding that. that is a non trivial task and it is fixing other more important things (unicode correctness!) than this...
Given that, I don't actually expect this issue to ever be fixed.
IMNSHO: People shouldn't abuse regexes and get themselves into this situation in the first place. ;)
discussion should really happen on python-ideas.