etcd is a distributed key-value store for the data of a distributed system. Prior to versions 3.4.26 and 3.5.9, the LeaseTimeToLive API allows access to key names (not value) associated to a lease when `Keys` parameter is true, even a user doesn't have read permission to the keys. The impact is limited to a cluster which enables auth (RBAC). Versions 3.4.26 and 3.5.9 fix this issue. There are no known workarounds.