CVE-2026-80274

Validating resolver can abort while caching a mismatched NOQNAME proof

Public exploit available. Not confirmed exploited in the wild yet. A vendor fix is available.

CVSS 3.17.5High EPSS percentile50th0.7% chance in 30 days CISA KEVNot listedNo confirmed exploitation
Public exploit: 0 sources FixVendor fixNo build named by the sources

Published 2026-09-16Updated 2026-09-17Sources: CVE.org, NVD

NVD CVE.org

What to do

The vendor has published a fix. Version details are below where the sources state them.

Steps

Written by AI from the record

Check the installed BIND 9 version with named -v and compare it with the affected versions in the advisory.
Upgrade a standard 9.20 installation to 9.20.29, a 9.21 installation to 9.21.26, or an S1 installation to 9.20.29-S1.
Restart BIND 9 after the upgrade and confirm DNS lookups work from both internal systems and the internet-facing services that rely on it.
If you run an older 9.11 through 9.18 release, arrange a supported-version upgrade with your DNS provider or administrator because no temporary workaround is known.

Vendor advisory Some work to apply

Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

If a BIND resolver sends a query for a DNSSEC-signed authoritative zone, and the authoritative server replies with a valid wildcard answer and signed NSEC3 proof, followed by an unsigned NSEC at the same owner name, it will trigger an unexpected program exit. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

In plain language

Written by AI from the record

BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1 can be crashed remotely, so small businesses running their own DNS resolver should act now.

Unauthenticated network denial of service in BIND 9 validating resolvers: a crafted DNSSEC response with mismatched NOQNAME proof data can trigger an unexpected process exit.

If you're affected

DNS service outage
Website access disruption
Email delivery disruption
Internal network disruption

What is it

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.

Who is affected

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.

How urgent is it

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.

What to do — in detail

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.

Technical context

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.

This is a general assessment based on public vulnerability data. It does not account for your specific infrastructure — when in doubt, consult a security specialist.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS50th

Public exploit

CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

0 sources with a proof of concept or module.

Exploit links, PoCs and Metasploit modules after sign-in

EPSS

0.7% chance of exploitation activity in the next 30 days, which ranks it in the 50th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Attention now

Rising, driven by in-the-wild reports.

Lifecycle

12 events over 1 day, from the signal feeds we watch.

2026-09-17Patch availableworkaround available, record updated
2026-09-16Patch availablepatch available, workaround available, workaround available, published, weakness classified, att&ck mapped, record updated, record updated

Affected products

ISCcommercial · USaka internet systems consortium
- BIND 9Networking Infrastructure

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Scored 7.5 by NVD.

How it is reached

Attack Vector NetworkExploitable remotely over the network without any special conditions
Attack Complexity LowNo special conditions — the attack can be reliably reproduced
Privileges Required NoneNo authentication required — anyone can exploit this
User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

Confidentiality NoneNo confidentiality impact
Integrity NoneNo integrity impact
Availability HighTotal denial of service — the component is completely unavailable