VCWN-06-000043 - Passwords must contain at least one special character.
To enforce the use of complex passwords, minimum numbers of characters of different classes are mandated. The use of complex passwords reduces the ability of attackers to successfully obtain valid passwords using guessing or exhaustive search techniques. Complexity requirements increase the password search space by requiring users to construct passwords from a larger character set than they may otherwise use. NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
From the vSphere Web Client go to Administration >> Single Sign-On >> Configuration >> Policies >> Password Policy. Click Edit. Set Special Characters to at least 1 and click OK.