CVE-2018-5734: A malformed request can trigger an assertion failure in badcache.c

Michael McNally mcnally at
Wed Feb 28 18:22:38 UTC 2018

While we are posting it in this public announcement forum (as is our
process for handling all security vulnerabilities in BIND) please note
that the following security advisory applies ONLY to several releases
in BIND 9 Supported Preview Edition, a special feature preview version
of BIND that is provided to eligible ISC support customers but not
released publicly.

Unless you are running a version of BIND that is built from a Supported
Preview Edition release this vulnerability disclosure should not apply
to you and may be safely disregarded.

If you are uncertain what version of BIND you are running --
all modern versions of BIND should report their version and build info
if you invoke the server with the "-V" argument, i.e. "named -V"
If your version information does not match one of the release versions
listed in the "Versions affected" field below then you are not affected.


CVE:                 CVE-2018-5734
Document Version:    2.0
Posting date:        28 Feb 2018
Program Impacted:    BIND
Versions affected:   9.10.5-S1 to 9.10.5-S4, 9.10.6-S1, 9.10.6-S2
Severity:            High
Exploitable:         Remotely


   While handling a particular type of malformed packet BIND
   erroneously selects a SERVFAIL rcode instead of a FORMERR rcode.
   If the receiving view has the SERVFAIL cache feature enabled,
   this can trigger an assertion failure in badcache.c when the
   request doesn't contain all of the expected information.


   Servers running the affected versions (9.10.5-S1 to 9.10.5-S4,
   9.10.6-S1, and 9.10.6-S2) are vulnerable if they allow recursion,
   unless the SERVFAIL cache is disabled for the receiving view.

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

For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:


   Disabling the SERVFAIL cache with 'servfail-ttl 0;' will prevent
   taking the code path that leads to the assertion failure.

Active exploits:

   No known active exploits.


   Upgrade to the patched release.  No publicly released versions of
BIND are affected

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

   -  BIND 9 version 9.10.6-S3

Document Revision History:

   1.0 Advance Notification 20 February, 2018
   2.0 Public Disclosure 28 February, 2018

Related Documents:

   See our BIND9 Security Vulnerability Matrix at for a complete listing of
   Security Vulnerabilities and versions affected.

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Advance Security Notifications, please visit

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   ISC patches only currently supported versions. When possible we
   indicate EOL versions affected.  (For current information on
   which versions are actively supported, please see

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   Details of our current security advisory policy and practice can
   be found here:

This Knowledge Base article is
the complete and official security advisory document.

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