Authorization Bypass Through User-Controlled Key vulnerability in
Apache ZooKeeper. If SASL Quorum Peer authentication is enabled
in ZooKeeper (quorum.auth.enableSasl=true), the authorization is
done by verifying that the instance part in SASL authentication ID
is listed in zoo.cfg server list. The instance part in SASL auth
ID is optional and if it's missing, like 'eve@EXAMPLE.COM',
the authorization check will be skipped.As a result an arbitrary
endpoint could join the cluster and begin propagating counterfeit
changes to the leader, essentially giving it complete read-write
access to the data tree.Quorum Peer authentication is not enabled
by default.
Users are recommended to upgrade to version 3.9.1, 3.8.3, 3.7.2,
which fixes the issue.
Alternately ensure the ensemble election/quorum communication is
protected by a firewall as this will mitigate the issue.
See the documentation for more details on correct cluster administration.