Check: SRG-APP-000516-DNS-000110
Domain Name System (DNS) SRG:
SRG-APP-000516-DNS-000110
(in versions v3 r2 through v2 r4)
Title
The platform on which the name server software is hosted must be configured to send outgoing DNS messages from a random port. (Cat II impact)
Discussion
OS configuration practices as issued by the US Computer Emergency Response Team (US CERT) and the National Institute of Standards and Technology's (NIST's) National Vulnerability Database (NVD), based on identified vulnerabilities that pertain to the application profile into which the name server software fits, should be always followed. In particular, hosts that run the name server software should not provide any other services and therefore should be configured to respond to DNS traffic only. In other words, the only allowed incoming ports/protocols to these hosts should be 53/udp and 53/tcp. Outgoing DNS messages should be sent from a random port to minimize the risk of an attacker guessing the outgoing message port and sending forged replies.
Check Content
Review the DNS configuration. Determine if a static port is being used to send outgoing DNS messages or whether it is configured to use a random port. If the DNS configuration specifies a static port to be used for outgoing DNS messages rather than a random port, this is a finding.
Fix Text
Configure the DNS server to use a random port for outgoing DNS messages.
Additional Identifiers
Rule ID: SV-205248r879887_rule
Vulnerability ID: V-205248
Group Title: SRG-APP-000516
Expert Comments
CCIs
Number | Definition |
---|---|
CCI-000366 |
The organization implements the security configuration settings. |
Controls
Number | Title |
---|---|
CM-6 |
Configuration Settings |