CVE: CVE-2026-78301
Title: Out-of-zone database nodes can become authoritative zone cuts
Document version: 2.0
Posting date: 16 September 2026
Program impacted: BIND 9
Versions affected:
BIND
- 9.11.0 -> 9.18.50
- 9.20.0 -> 9.20.27
- 9.21.0 -> 9.21.25
BIND Supported Preview Edition
- 9.11.3-S1 -> 9.18.50-S1
- 9.20.9-S1 -> 9.20.27-S1
Severity: Medium
Exploitable: Remotely
Description:
A malformed zone may contain an NS or DNAME node above its origin, which named treats as a zone cut. If an attacker inserts a malformed zone into a BIND authoritative server (e.g., via zone transfer), queries for names inside the configured zone then lose authoritative status and return an out-of-zone delegation. On a server that also provides recursion BIND can follow this locally sourced cut and cache attacker-supplied data, affecting names outside the configured zone. This situation persists as long as the malformed zone remains in the zone database.
Impact:
In a successful attack on an authoritative server that is also a resolver, cache poisoning may occur with attacker supplied records. A purely authoritative server may return bogus attacker-supplied referrals to queries but without the AA flag.
CVSS Score: 5.8
CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:H/A:N
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:H/PR:H/UI:N/S:C/C:N/I:H/A:N&version=3.1.
Workarounds:
No workarounds known.
Active exploits:
We are not aware of any active exploits.
Solution:
Upgrade to the patched release most closely related to your current version of BIND 9:
- 9.20.29
- 9.21.26
BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.
- 9.20.29-S1
Acknowledgments:
ISC would like to thank Henrique Pereira for bringing this vulnerability to our attention.
Document revision history:
- 1.0 Early Notification, 9 September 2026
- 1.1 Revised the list of fixed versions, 11 September 2026
- 2.0 Public disclosure, 16 September 2026
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 be posted as confidential GitLab issues at:
https://gitlab.isc.org/isc-projects/bind9/-/issues/new?issue[confidential]=true
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-2026-78301 is the complete and official security advisory document.
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