Improper restriction of excessive authentication attempts in the WAMP-CRA (challenge-response) authentication path in Zenitel Connect before 1.11.0 allows remote attackers to guess user passwords via unlimited authentication attempts, because the path, in which the broker issues a challenge and the client returns an HMAC of it keyed with the user's secret, applies no account lockout or rate limiting. Affected releases enforce a password policy of at least 12 characters including upper-case, lower-case, numeric and special characters, so practical exploitation requires a reused or predictable password rather than exhaustive guessing. The WAMP-CRA authentication path is removed in 1.11.0.