The Windows DNS Server's zone files must not include CNAME records pointing to a zone with lesser security for more than six months.
An XCCDF Rule
Description
<VulnDiscussion>The use of CNAME records for exercises, tests, or zone-spanning (pointing to zones with lesser security) aliases should be temporary (e.g., to facilitate a migration) and not be in place for more than six months. 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 lookup after obtaining the canonical name. In the case of an authoritative name server, this information is promulgated throughout the enterprise to caching servers, which compounds the vulnerability.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-259359r961863_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Remove any zone-spanning CNAME records that have been active for more than six months, which are not supporting zone delegations, CNAME records supporting a system migration, or CNAME records pointing to third-party CDNs or cloud computing platforms.
In the case of third-party CDNs or cloud offerings, an approved mission need must be demonstrated (AO approval of use of a commercial cloud offering would satisfy this requirement).