Product Affected

This issue can affect all Junos devices with the DNSSEC security extension enabled.
High
7.8 (AV:N/AC:L/Au:N/C:N/I:N/A:C)

Problem


BIND stores a cache of query names that are known to be failing due to misconfigured name servers or a broken chain of trust. Under high query loads, when DNSSEC validation is active, it is possible for a condition to arise in which data from this cache of failing queries could be used before it was fully initialized, triggering an assertion failure.

An attacker that is able to generate high volume of DNSSEC validation enabled queries can trigger the assertion failure that causes it to crash, resulting in a denial of service.

This issue only affects Junos devices with DNSSEC enabled, using the ' set system services dns dnssec ' configuration option.

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

Solution


All Junos OS software releases built on or after 2013-02-13 have fixed this specific issue. Releases containing the fix specifically include: 10.4R13, 11.4R6, 11.4X27.43 (MX BBE), 12.1R5, 12.1X44-D15 (SRX), 12.2R3, 12.3X50-D11 (ACX), 12.3R1, and all subsequent releases (i.e. all releases built after 12.3R1).

Customers can confirm the build date of any Junos OS release by issuing the command ' show version detail '.

This issue is being tracked as PR 806838 and is visible on the Customer Support website.

KB16765 [juniper.net] - "In which releases are vulnerabilities fixed?" describes which release vulnerabilities are fixed as per our End of Engineering and End of Life support policies.


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.

Workaround


While DNS resolution is most often used during CLI command processing, customers who do not require DNSSEC may disable the security extension by typing:

user@junos# delete system services dns dnssec

Additionally, use access lists or firewall filters to limit access to the router via SSH or telnet only from trusted hosts.

Severity Assessment

Information for how Juniper Networks uses CVSS can be found at KB 16446 [juniper.net] "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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