Regex

A vulnerability exists in Perl versions up to and including 5.43.9 where regular expression matches can be silently incorrect when an alternation of more than 65535 fixed string branches is compiled into a trie within the Perl_study_chunk function, potentially leading to incorrect logic or data processing.

CVE-2026-4926 describes a denial-of-service vulnerability due to an inefficient regular expression complexity issue when handling multiple sequential optional groups, leading to exponential growth and resource exhaustion.

Jupyter Server versions 2.17.0 and earlier are vulnerable to a CORS origin validation bypass due to improper use of `re.match()` in validating the Origin header against the `allow_origin_pat` configuration, allowing attackers to bypass CORS restrictions.