CVE-2017-3142: An error in TSIG authentication can permit unauthorized zone transfers

[Michael McNally]

CVE:                 CVE-2017-3142
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:            Medium
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 may be able to circumvent TSIG authentication of AXFR
   requests via a carefully constructed request packet.  A server
   that relies solely on TSIG keys for protection with no other ACL
   protection could be manipulated into:

   -  providing an AXFR of a zone to an unauthorized recipient
   -  accepting bogus NOTIFY packets

Impact:

    An unauthorized AXFR (full zone transfer) permits an attacker
    to view the entire contents of a zone.  Protection of zone
    contents is often a commercial or business requirement.

    If accepted, a NOTIFY sets the zone refresh interval to 'now'.
    If there is not already a refresh cycle in progress then named
    will initiate one by asking for the SOA RR from its list of
    masters.  If there is already a refresh cycle in progress, then
    named will queue the new refresh request.  If there is already
    a queued refresh request, the new NOTIFY will be discarded.
    Bogus notifications can't be used to force a zone transfer from
    a malicious server, but could trigger a high rate of zone refresh
    cycles.

CVSS Score:          5.3
CVSS Vector:         CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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:L/I:N/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-ACLs-with-both-addresses-and-keys.html.

   (Note that this technique may not be effective against bogus
   NOTIFY packets if an attacker is able to reach the target DNS
   server whilst using a spoofed sending address).

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 Correct Notify to NOTIFY; Update phrasing in Workarounds section;
       Update phrasing in Description; Correct date of similar public
       announcement, 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:

   ISC patches only currently supported versions. When possible we
   indicate EOL versions affected.  (For current information on
   which versions are actively supported, please see
   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-01504 is
the complete and official security advisory document.

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