I suggest closing this as "wontfix".

This is a just an non-optimized regexp pattern leading to long run times.  That these are possible is a well-known trait of backtracking regular expression engines in general, and ours in particular.

IMO this isn't a security issue since the root of the issue is the pattern.  I don't see this as a bug or a significant performance issue either, and there is no concrete enhancement suggestion here.

For clarification, the given pattern is equivalent to:
pat = r'''^
(
\(?
[\w\d\-\.\\]{3,}
\|?
)+
[\w\d\-\.\\]{3,}
\)?
$'''