CVE:                 CVE-2020-8621
Document version:    2.0
Posting date:        20 August 2020
Program impacted:    BIND
Versions affected:   BIND 9.14.0 -> 9.16.5, 9.17.0 -> 9.17.3
Severity:            Medium
Exploitable:         Remotely


   While query forwarding and QNAME minimization are mutually incompatible,
   BIND did sometimes allow QNAME minimization when continuing with recursion
   after 'forward first' did not result in an answer.  In these cases the data
   used by QNAME minimization might be inconsistent, leading to an assertion
   failure, causing the server to exit.


   If a server is configured with both QNAME minimization and 'forward first'
   then an attacker who can send queries to it may be able to trigger the
   condition that will cause the server to crash.

   Servers that 'forward only' are not affected.

CVSS Score: 6.7

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


   No workarounds known.

Active exploits:

   We are not aware of any active exploits.


   Upgrade to the patched release most closely related to your current version
   of BIND:

   - BIND 9.16.6
   - BIND 9.17.4


   ISC would like to thank Joseph Gullo for bringing this vulnerability  to our

Document revision history:

   1.0 Early Notification, 12 August 2020
   1.1 Updated Posting Date, 17 August 2020
   2.0 Public Announcement, 20 August 2020

Related documents:

   See our BIND 9 Security Vulnerability Matrix for a complete listing of
   security vulnerabilities and versions affected.

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   EOL versions affected.  (For current information on which versions are
   actively supported, please see

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