CVE-2026-80274

This is a flaw in software that answers DNS requests, which are the lookups computers use to find websites and services. A malicious DNS reply can make that software stop running, like sending a specially prepared form that causes a receptionist to close the front desk for everyone.

This matters to you if your business runs bind 9 as its own DNS resolver, including on a server, firewall, or managed network appliance. It is especially relevant where that resolver handles DNS lookups for staff, business systems, websites, or email. The issue is only a risk when bind 9 is configured to validate signed DNS information and queries the affected signed zone pattern.

A public exploit is available, so an attacker can use this flaw to try to interrupt DNS service without needing an account. There are no reported real-world incidents at this time, but the exposed service can be crashed remotely and no workaround is known, which makes this a red-priority update.

Confirm whether named -v reports an affected build and whether the server is operating as a validating resolver. For supported branches, target 9.20.29 for the standard 9.20 branch, 9.21.26 for the 9.21 branch, and 9.20.29-S1 for the S1 branch; use your operating-system or vendor package channel where it supplies these releases.

Back up the current configuration, apply the normal package or vendor upgrade, restart the named service, and test recursive lookups from a client that uses the resolver. Older 9.11–9.18 deployments need a migration plan to a patched supported release; review local configuration compatibility before changing major branches.

No temporary workaround is known. CISA has not added this CVE to the Known Exploited Vulnerabilities catalog, so there is no CISA remediation due date. After deployment, watch service availability, named restart events, and resolver logs for unexpected exits or unusual malformed DNS response handling.

CVE-2026-80274 is rated CVSS 7.5 High (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and maps to CWE-617, reachable assertion. A network attacker can provide or reflect a crafted response containing the required signed and unsigned DNS record combination to a validating resolver querying a DNSSEC-signed authoritative zone, causing an unexpected exit. A public exploit is available. EPSS is 0.5% with a flat trend (41st percentile); this is a prediction, not evidence of active exploitation. The CVE is not in CISA KEV, and ISC reports no known exploitation in the wild.