GitPython's Actor.name_email_regex regular expression is vulnerable to catastrophic backtracking (ReDoS) when parsing commit author or committer headers containing a long string with an unterminated '<'. This causes the Python regex engine to consume CPU time quadratically relative to input length, leading to denial of service. The vulnerability affects any GitPython API call that reads commit author or committer metadata, including CI runners and code-hosting backends processing untrusted repositories. The regex pattern '(.*) <(.*?)>' triggers excessive backtracking when the input lacks a closing '>'.