etcd before versions 3.3.23 and 3.4.10 does not perform any password length validation, which allows for very short passwords, such as those with a length of one. This may allow an attacker to guess or brute-force users' passwords with little computational effort.
https://github.com/etcd-io/etcd/security/advisories/GHSA-4993-m7g5-r9hh