In memcached before 1.6.42, username data for SASL password database authentication has a timing side channel because a loop exits as soon as a valid username is found by sasl_server_userdb_checkpass.
2. memcached: memcached: Username enumeration via timing side channel
A flaw was found in memcached. A remote attacker can exploit a timing side channel during Simple Authentication and Security Layer (SASL) password database authentication. This vulnerability allows an attacker to observe subtle timing differences, which could be used to enumerate valid usernames.