UBUNTU-CVE-2026-81736: High severity ubuntu/isc-dhcp vulnerability

Q: Which deployments are exposed to this issue?

BIND resolvers running affected BIND 9 versions are exposed. The affected ranges are 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.18.11-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

Q: What does an attacker need to do to trigger the CPU exhaustion?

The resolver must first have cached a tree of SVCB/HTTPS AliasMode records. A query for the root of that cached tree then causes the resolver to spend disproportionate CPU time constructing its response.

Q: What is the practical impact of successful exploitation?

The issue can cause high CPU consumption in the resolver, creating a denial-of-service condition. The supplied severity vector indicates network reachability, low attack complexity, and no required privileges or user interaction.

Published Sep 16, 2026

Updated

If a BIND resolver has cached a tree of SVCB/HTTPS AliasMode records, and is then queried for the root of that tree, the resolver will spend disproportionate CPU time constructing the response. This issue affects BIND 9 versions 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.18.11-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

Affected Software

10 affected componentsFixes available

ubuntu/isc-dhcp*

ubuntu/bind9<1:9.18.30-0ubuntu0.20.04.2+esm3

1:9.18.30-0ubuntu0.20.04.2+esm3

ubuntu/bind9-libs*

ubuntu/bind9<1:9.18.39-0ubuntu0.22.04.7

1:9.18.39-0ubuntu0.22.04.7

ubuntu/bind9-libs*

ubuntu/bind9<1:9.18.39-0ubuntu0.24.04.8

1:9.18.39-0ubuntu0.24.04.8

ubuntu/isc-dhcp*

ubuntu/bind9<1:9.20.24-1ubuntu3.1

1:9.20.24-1ubuntu3.1

ubuntu/bind9<1:9.20.24-1ubuntu0.4

1:9.20.24-1ubuntu0.4

ubuntu/isc-dhcp*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/bind9 to a version that resolves this vulnerability.
Fixed in 1:9.18.30-0ubuntu0.20.04.2+esm3
Upgrade
Upgrade ubuntu/bind9 to a version that resolves this vulnerability.
Fixed in 1:9.18.39-0ubuntu0.22.04.7
Upgrade
Upgrade ubuntu/bind9 to a version that resolves this vulnerability.
Fixed in 1:9.18.39-0ubuntu0.24.04.8
Upgrade
Upgrade ubuntu/bind9 to a version that resolves this vulnerability.
Fixed in 1:9.20.24-1ubuntu3.1
Upgrade
Upgrade ubuntu/bind9 to a version that resolves this vulnerability.
Fixed in 1:9.20.24-1ubuntu0.4

Event History

Sep 16, 2026

CVE Published

via OSV·02:17 PM

Data Sourced

via OSV·02:17 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

Which deployments are exposed to this issue?

BIND resolvers running affected BIND 9 versions are exposed. The affected ranges are 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.18.11-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

What does an attacker need to do to trigger the CPU exhaustion?

The resolver must first have cached a tree of SVCB/HTTPS AliasMode records. A query for the root of that cached tree then causes the resolver to spend disproportionate CPU time constructing its response.

What is the practical impact of successful exploitation?

The issue can cause high CPU consumption in the resolver, creating a denial-of-service condition. The supplied severity vector indicates network reachability, low attack complexity, and no required privileges or user interaction.

UBUNTU-CVE-2026-81736: High severity ubuntu/isc-dhcp vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

Which deployments are exposed to this issue?

What does an attacker need to do to trigger the CPU exhaustion?

What is the practical impact of successful exploitation?

Company

Resources

Contact

Frequently Asked Questions

Which deployments are exposed to this issue?

What does an attacker need to do to trigger the CPU exhaustion?

What is the practical impact of successful exploitation?