CVE: CVE-2022-0635
Document version: 2.0
Posting date: 16 March 2022
Program impacted: BIND
Versions affected: BIND 9.18.0
Severity: High
Exploitable: Remotely
Description:
We refactored the RFC 8198 Aggressive Use of DNSSEC-Validated
Cache feature (synth-from-dnssec) for the new BIND 9.18.0 stable
release, and changed the default so that is now automatically
enabled for dnssec-validating resolvers. Subsequently it was found
that repeated patterns of specific queries to servers with this
feature enabled could cause an INSIST failure in
query.c:query_dname which causes named to terminate unexpectedly.
The vulnerability affects BIND resolvers running 9.18.0 that have
both `dnssec-validation` and `synth-from-dnssec` enabled. (Note that
`dnssec-validation auto;` is the default setting unless
configured otherwise in `named.conf` and that enabling
`dnssec-validation` automatically enables `synth-from-dnssec`
unless explicitly disabled)
Impact:
When a vulnerable version of named receives a series of specific
queries, the named process will eventually terminate due to a
failed assertion check.
CVSS Score: 7.0
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C
For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C&version=3.1
Workarounds:
The failure can be avoided by adding this option to named.conf:
synth-from-dnssec no;
However we do not recommend disabling this feature other than as a
temporary workaround because it provides protection from
pseudo-random-subdomain attacks against DNSSEC-signed zones.
Active exploits:
We are not aware of any active exploits.
Solution:
Users of BIND 9.18.0 should upgrade to BIND 9.18.1
Acknowledgments:
ISC would like to thank Vincent Levigneron of AFNIC for reporting
this issue to us and for verifying the fix and workaround.
Document revision history:
1.0 Early Notification, 9 March 2022
2.0 Public disclosure, 16 March 2022
Related documents:
See Operational Notification "synth-from-dnssec may cause slow
resolution on resolvers under certain cache conditions" for more
information regarding early BIND support for RFC 8198 Aggressive Use of
DNSSEC-Validated Cache and our recommendation that this feature be
disabled until versions of BIND were made available which contain an
improvement to the synth-from-dnssec feature:
https://kb.isc.org/docs/operational-notification-synth-from-dnssec-may-cause-slow-resolution-on-resolvers-under-certain-cache-conditions
See our BIND 9 Security Vulnerability Matrix for a complete listing of
security vulnerabilities and versions affected:
https://kb.isc.org/docs/aa-00913
Do you still have questions? Questions regarding this advisory should go
to security-offi...@isc.org. To report a new issue, please encrypt your
message using security-offi...@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: https://www.isc.org/reportbug/.
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 https://www.isc.org/download/.)
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-2022-0635 is
the complete and official security advisory document.
Legal Disclaimer:
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