CVE-2026-106454: Twisted: IMAP wildcardToRegexp() ReDoS

wildcardToRegexp() in twisted/mail/imap4.py converts IMAP LIST/LSUB wildcard patterns to Python regular expressions. It substitutes the two IMAP wildcards (* → (?:.*?) and % → (?:(?:[^\\/])*?)) but passes every other character through unchanged to re.compile(). This means that an authenticated IMAP client can send a quoted pattern string containing arbitrary regex syntax - including catastrophic-backtracking constructs such as (a+)+z.

Because Twisted runs a cooperative, single-threaded reactor, a blocking regex match freezes all I/O on the server for the duration of the match.