CVE-2017-3143: An error in TSIG authentication can permit unauthorized dynamic updates

[Michael McNally]

CVE:                 CVE-2017-3143
Document Version:    2.0
Posting date:        29 June 2017
Program Impacted:    BIND
Versions affected:   9.4.0 -> 9.8.8, 9.9.0 -> 9.9.10-P1, 9.10.0 ->
9.10.5-P1,
                     9.11.0 -> 9.11.1-P1, 9.9.3-S1 -> 9.9.10-S2,
                     9.10.5-S1 -> 9.10.5-S2
Severity:            High
Exploitable:         Remotely

Description:

    An attacker who is able to send and receive messages to an
    authoritative DNS server and who has knowledge of a valid TSIG
    key name for the zone and service being targeted may be able
    to manipulate BIND into accepting an unauthorized dynamic update.

Impact:

    A server that relies solely on TSIG keys with no other address-based
    ACL protection could be vulnerable to malicious zone content
    manipulation using this technique.

CVSS Score:          7.5
CVSS Vector:         CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Workarounds:

    The effects of this vulnerability can be mitigated by using
    Access Control Lists (ACLs) that require both address range
    validation and use of TSIG authentication in conjunction.  For
    information on how to configure this type of compound authentication
    control, please see:
https://kb.isc.org/article/AA-00723/0/Using-Access-Control-Lists

    Administrators who have made use of named.conf option "update-policy
    local;" should refer to the Administrator Reference Manual (ARM)
    for details of the automatic update policy that will be established
    and to assess whether or not this conveys any additional risk
    to their server.  (Note that this option is not enabled by
    default).

Active exploits:

    No known active exploits but a similar issue was announced
    publicly on 23 June 2017 by another DNS server software provider.

Solution:

    Upgrade to the patched release most closely related to your
    current version of BIND. These can all be downloaded from
    http://www.isc.org/downloads.

    -  BIND 9 version 9.9.10-P2
    -  BIND 9 version 9.10.5-P2
    -  BIND 9 version 9.11.1-P2

    BIND Supported Preview Edition is a special feature preview
    branch of BIND provided to eligible ISC support customers.

    -  BIND 9 version 9.9.10-S3
    -  BIND 9 version 9.10.5-S3

Acknowledgements:

   ISC would like to thank Clément Berthaux from Synacktiv for
   reporting this issue.

Document Revision History:

   1.0 Advance Notification 26 June 2017
   1.1 CVSS score corrected (was previously erroneously listed
       as 7.8) 27 June 2017
   1.2 Update phrasing in the Workarounds section; Correct date of similar
       public announcement, 29 June 2017
   1.3 Remove references to SIG(0), which is not affected, 29 June 2017
   2.0 Public disclosure 29 June 2017

Related Documents:

   See our BIND9 Security Vulnerability Matrix at
   https://kb.isc.org/article/AA-00913 for a complete listing of
   Security Vulnerabilities and versions affected.

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Note:

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   http://www.isc.org/downloads/).

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   Details of our current security advisory policy and practice can
   be found here: https://kb.isc.org/article/AA-00861

This Knowledge Base article https://kb.isc.org/article/AA-01503 is
the complete and official security advisory document.

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