CVE-2016-4423

The attemptAuthentication function in
Component/Security/Http/Firewall/UsernamePasswordFormAuthenticationListener.php
in Symfony before 2.3.41, 2.7.x before 2.7.13, 2.8.x before 2.8.6, and
3.0.x before 3.0.6 does not limit the length of a username stored in a
session, which allows remote attackers to cause a denial of service
(session storage consumption) via a series of authentication attempts with
long, non-existent usernames.