CVE-2021-25215: An assertion check can fail while answering queries for DNAME records that require the DNAME to be processed to resolve itself
mcnally at isc.org
Wed Apr 28 20:20:01 UTC 2021
Document version: 2.0
Posting date: 28 April 2021
Program impacted: BIND
Versions affected: BIND 9.0.0 -> 9.11.29, 9.12.0 -> 9.16.13, and versions
BIND 9.9.3-S1 -> 9.11.29-S1 and 9.16.8-S1 -> 9.16.13-S1
of BIND Supported Preview Edition, as well as release
versions 9.17.0 -> 9.17.11 of the BIND 9.17 development
DNAME records, described in RFC 6672, provide a way to redirect
a subtree of the domain name tree in the DNS. A flaw in the way
named processes these records may trigger an attempt to add the
same RRset to the ANSWER section more than once. This causes an
assertion check in BIND to fail.
DNAME records are processed by both authoritative and recursive
servers. For authoritative servers, the DNAME record triggering
the flaw can be retrieved from a zone database. For servers
performing recursion, such a record is processed in the course
of a query sent to an authoritative server.
When a vulnerable version of named receives a query for a record
triggering the flaw described above, the named process will
terminate due to a failed assertion check.
The vulnerability affects all currently maintained BIND 9 branches
(9.11, 9.11-S, 9.16, 9.16-S, 9.17) as well as all other versions
of BIND 9.
CVSS Score: 7.5
CVSS Vector: CVSS:3.1/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:
No workarounds known.
We are not aware of any active exploits.
Upgrade to the patched release most closely related to your current
version of BIND:
- BIND 9.11.31
- BIND 9.16.15
- BIND 9.17.12
BIND Supported Preview Edition is a special feature preview branch
of BIND provided to eligible ISC support customers.
- BIND 9.11.31-S1
- BIND 9.16.15-S1
ISC would like to thank Siva Kakarla for bringing this vulnerability to our attention.
Document revision history:
1.0 Early Notification, 14 April 2021
1.1 Disclosure schedule change, 15 April 2021
2.0 Public disclosure, 28 April 2021
See our BIND 9 Security Vulnerability Matrix for a complete
listing of security vulnerabilities and versions affected.
Do you still have questions? Questions regarding this advisory
should go to security-officer at isc.org. To report a new issue, please
encrypt your message using security-officer at isc.org's PGP key which
can be found here: https://www.isc.org/pgpkey/. If you are unable
to use encrypted email, you may also report new issues at:
ISC patches only currently supported versions. When possible we
indicate EOL versions affected. (For current information on which
versions are actively supported, please see
ISC Security Vulnerability Disclosure Policy:
Details of our current security advisory policy and practice can
be found in the ISC Software Defect and Security Vulnerability
Disclosure Policy at https://kb.isc.org/docs/aa-00861.
The Knowledgebase article https://kb.isc.org/docs/cve-2021-25215
is the complete and official security advisory document.
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