CVE-2020-8624: update-policy rules of type "subdomain" are enforced incorrectly

CVE: CVE-2020-8624

Document version: 2.0

Posting date: 20 August 2020

Program impacted: BIND

Versions affected: BIND 9.9.12 -> 9.9.13, 9.10.7 -> 9.10.8, 9.11.3 -> 9.11.21, 9.12.1 -> 9.16.5, 9.17.0 -> 9.17.3, also affects 9.9.12-S1 -> 9.9.13-S1, 9.11.3-S1 -> 9.11.21-S1 of the BIND 9 Supported Preview Edition

Severity: Low

Exploitable: Remotely

Description:

Change 4885 inadvertently caused "update-policy" rules of type "subdomain" to be treated as if they were of type "zonesub", allowing updates to all parts of the zone along with the intended subdomain.

Impact:

An attacker who has been granted privileges to change a specific subset of the zone's content could abuse these unintended additional privileges to update other contents of the zone.

CVSS Score: 3.9

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N/E:P/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:L/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C&version=3.1.

Workarounds:

No workarounds known.

Active exploits:

We are not aware of any active exploits but the issue has been described on a public bug tracker for a Linux distribution.

Solution:

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

• BIND 9.11.22
• BIND 9.16.6
• BIND 9.17.4

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

• BIND 9.11.22-S1

Acknowledgments: ISC would like to thank Joop Boonen of credativ GmbH for bringing this vulnerability to our attention.

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.

Do you still have questions? Questions regarding this advisory should go to security-officer@isc.org. To report a new issue, please encrypt your message using security-officer@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-2020-8624 is the complete and official security advisory document.

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