named in ISC BIND allows remote attackers to cause a denial of service (assertion failure and daemon exit) via a DNAME record in the answer section of a response to a recursive query, related to db.c and resolver.c.
named in ISC BIND 9.x before 9.9.9-P5, 9.10.x before 9.10.4-P5, and 9.11.x before 9.11.0-P2 allows remote attackers to cause a denial of service (assertion failure and daemon exit) via a crafted DS resource record in an answer.
These issues only affect devices where DNS proxy service is enabled.
DNS proxy feature is disabled by default.
Juniper SIRT is not aware of any malicious exploitation of these vulnerabilities on Juniper products.
CVE-2016-2776 and CVE-2016-8864 have been addressed in Junos OS 12.1X46-D65, 12.3X48-D45, 15.1X49-D70 and all subsequent releases.
CVE-2016-9131, CVE-2016-9147 and CVE-2016-9444 have been addressed in Junos OS 12.1X46-D66, 12.3X48-D50, 15.1X49-D80 and all subsequent releases.
This issues are being tracked as PR 1219438, 1228678 and 1245686 and are visible on the Customer Support website.
DNS proxy service may be disabled to workaround all these issues.
You may view the status of DNS proxy service via the command:
show system services dns-proxy statistics
DNS proxy statistics :
Status : enabled
Accepting DNS queries only from trusted network would mitigate CVE-2016-2776 which requires a malicious client side request to trigger the named crash.
Firewall filters limiting receipt of DNS queries on TCP and UDP port 53 can be implemented for different hosted groups of DNS servers; external DNS servers should be separate from internal DNS servers. External DNS servers should only accept DNS queries from internal DNS servers and reject externally facing DNS queries if using BIND.
A layered approach utilizing non-BIND based DNS servers may be taken as well; non-BIND servers can be deployed for externally hosted domains, and servers using BIND can be deployed internally.
In addition to the recommendations listed above, it is a good security practice to limit the exploitable attack surface of critical infrastructure networking equipment. Use access lists or firewall filters to limit access to the devices only from trusted, administrative networks or hosts.