V-285253

Discussion

The use of CNAME records for exercises, tests, or zone-spanning aliases should be temporary (e.g., to facilitate a migration). When a host name is an alias for a record in another zone, an adversary has two points of attack: the zone in which the alias is defined and the zone authoritative for the alias's canonical name. This configuration also reduces the speed of client resolution because it requires a second look up after obtaining the canonical name. Furthermore, in the case of an authoritative name server, this information is promulgated throughout the enterprise to caching servers and thus compounds the vulnerability.

Check Content

Verify zone-spanning CNAME records are no older than six months.

1. Navigate to Administration >> Logs >> Audit Log. Click "Show Filter" (if it is not already displayed). 
2. Create a new search using "Object Type", "equals", and "CNAME Record". 
3. Click the plus (+) symbol to add a second search parameter. 
4. Create an additional search parameter, "Timestamp before YYYY-MM-DD", using the calendar selection box to choose the appropriate date six months prior to the current date. 
5. Click "Apply" to display CNAME records created more than six months ago. 

If there are zone-spanning CNAME records older than six months and the CNAME records resolve to anything other than fully qualified domain names for glue records supporting zone delegations, CNAME records supporting a system migration, or CNAME records that point to third-party Content Delivery Networks (CDN) or cloud computing platforms with an authorizing official (AO)-approved and documented mission need, this is a finding.