CVE-2023-6680

An improper certificate validation issue in Smartcard authentication in
GitLab EE affecting all versions from 11.6 prior to 16.4.4, 16.5 prior to
16.5.4, and 16.6 prior to 16.6.2 allows an attacker to authenticate as
another user given their public key if they use Smartcard authentication.
Smartcard authentication is an experimental feature and has to be manually
enabled by an administrator.