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.

In etcd before versions 3.3.23 and 3.4.10, certain directory paths are created (etcd data directory and the directory path when provided to automatically generate self-signed certificates for TLS connections with clients) with restricted access permissions (700) by using the os.MkdirAll. This function does not perform any permission checks when a given directory path exists already. A possible workaround is to ensure the directories have the desired permission (700).

In etcd before versions 3.3.23 and 3.4.10, it is possible to have an entry index greater then the number of entries in the ReadAll method in wal/wal.go. This could cause issues when WAL entries are being read during consensus as an arbitrary etcd consensus participant could go down from a runtime panic when reading the entry.

In etcd before versions 3.3.23 and 3.4.10, a large slice causes panic in decodeRecord method. The size of a record is stored in the length field of a WAL file and no additional validation is done on this data. Therefore, it is possible to forge an extremely large frame size that can unintentionally panic at the expense of any RAFT participant trying to decode the WAL.