Hello Fergus,
The MongoDB configured on the Commserve/Web Servers is accessed using a Commvault back end account. These credentials are stored in the registry and Commserve database.
Commvault Support can decrypt the credentials if required. However, this would need a Support ticket to be created so an engineer may assist.
>As an additional note, you can configure Mongo to use TLS/SSL for secured access (if required by your security team) https://documentation.commvault.com/commvault/v11/article?p=1967.htm
Please let me know if you find this information helpful. If you have any further questions or concerns, I would be more than happy to assist.