Question:

What characters are allowed in Vault usernames and passwords?

Answer:

Usernames 

Vault usernames may include alphanumerical characters (A-Z and 0-9, case insensitive), as well as the following special characters:

• Exclamation mark ( ! )
• Number sign/Hash ( # )
• Dollar sign ( $ )
• Percent sign ( % )
• Ampersand ( & )
• Apostrophe ( ' )
• Asterisk ( * )
• Plus sign ( + )
• Hyphen-minus ( - )
• Slash ( / )
• Equal Sign ( = )
• Question Mark ( ? )
• Circumflex Accent ( ^ )
• Underscore/Low line ( _ )
• Grave accent ( ` )
• Left curly bracket ( { )
• Vertical bar ( | )
• Right curly bracket ( } )
• Tilde ( ~ )
• Period ( . )

Vault does not support:

• Other special characters, such as double-quotation marks ( " ).
• Any period/dot at the beginning or the end of the username.
• Any whitespace in the username.

Passwords

As for Vault passwords, only ASCII characters are allowed.

Related Documentation:

Vault Help Documentation: Creating and Managing Users