2016-01 Security Bulletin: Junos: Vulnerability in ISC BIND named (CVE-2015-5477)

Product Affected:This issue can affect any SRX-Series and J-Series configured with DNS Proxy server services enabled.

Problem:A vulnerability in ISC BIND’s handling of queries for TKEY records may allow remote attackers to terminate the daemon process on an assertion failure. Juniper SIRT is not aware of any malicious exploitation of this issue on Junos devices.   The Juniper SIRT is aware of publicly available PoC exploits.This issue affects only SRX-Series and J-Series configured with DNS Proxy server services enabled.  This issue can affect both standalone and HA configurations.This issue has been assigned CVE-2015-5477.

Solution:The following software releases have been updated to resolve this specific issue: Junos OS 12.1X44-D55, 12.1X46-D40, 12.1X46-D45, 12.1X47-D30, 12.3R11, 12.3R12, 12.3X48-D20, 12.3X50-D50, 13.2R9, 13.2X51-D39, 13.2X51-D40, 13.3R8, 14.1R6, 14.1R7, 14.1X53-D30, 14.2R5, 15.1F3, 15.1R2, 15.1R3, 15.1X49-D30, 15.1X53-D20, 15.2R1 and all subsequent releases. Note:  To proactively mitigate this issue in the future, should DNS Server features be introduced into other Junos OS platforms and products, this issue is fixed in the other stated platforms other than the ones listed as vulnerable under this JSA. This BIND issue does affect, but these versions are not vulnerable to this issue, as enabling the DNS Server feature does not exists on these platforms. Should SRX-Series and J-Series releases assume R-releases in the future, these versions are fixed moving forward in these release trains as well.This issue is being tracked as PR 1108761 and is visible on the Customer Support website. KB16765 – “In which releases are vulnerabilities fixed?” describes which release vulnerabilities are fixed as per our End of Engineering and End of Life support policies.

Workaround:DNS proxy can be disabled; the following example set statements show if the service is enabled: set dns dns-proxy interface ge-0/0/1.0set dns dns-proxy default-domain * forwarders 172.17.28.100You may view the status of DNS proxy via the command: show system services dns dns-proxyFirewall 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.

Implementation:How to obtain fixed software: Security vulnerabilities in Junos are fixed in the next available Maintenance Release of each supported Junos version. In some cases, a Maintenance Release is not planned to be available in an appropriate time-frame. For these cases, Service Releases are made available in order to be more timely. Security Advisory and Security Notices will indicate which Maintenance and Service Releases contain fixes for the issues described. Upon request to JTAC, customers will be provided download instructions for a Service Release. Although Juniper does not provide formal Release Note documentation for a Service Release, a list of “PRs fixed” can be provided on request. Modification History: 2016-01-13: Initial publication

Related Links: CVSS Score:5.3 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)

Risk Level:Medium

Acknowledgements: 

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