CVE-2019-19234

In Sudo through 1.8.29, the fact that a user has been blocked (e.g., by using the ! character in the shadow file instead of a password hash) is not considered, allowing an attacker (who has access to a Runas ALL sudoer account) to impersonate any blocked user. NOTE: The software maintainer believes that this CVE is not valid. Disabling local password authentication for a user is not the same as disabling all access to that user–the user may still be able to login via other means (ssh key, kerberos, etc). Both the Linux shadow(5) and passwd(1) manuals are clear on this. Indeed it is a valid use case to have local accounts that are only accessible via sudo and that cannot be logged into with a password. Sudo 1.8.30 added an optional setting to check the shell of the target user (not the encrypted password!) against the contents of /etc/shells but that is not the same thing as preventing access to users with an invalid password hash