UBUNTU-CVE-2026-77119: Medium severity ubuntu/bind9 vulnerability

Published Sep 16, 2026
·
Updated

A validly signed NSEC3 from an unrelated sibling zone may be accepted as an insecurity proof, downgrading a secure delegation and letting a forged unsigned answer through. 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.

Affected Software

13 affected componentsFixes available
ubuntu/bind9<1:9.9.5.dfsg-3ubuntu0.19+esm15
1:9.9.5.dfsg-3ubuntu0.19+esm15
ubuntu/bind9<1:9.10.3.dfsg.P4-8ubuntu1.19+esm11
1:9.10.3.dfsg.P4-8ubuntu1.19+esm11
ubuntu/bind9<1:9.11.3+dfsg-1ubuntu1.19+esm6
1:9.11.3+dfsg-1ubuntu1.19+esm6
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.

  1. Upgrade

    Upgrade ubuntu/bind9 to a version that resolves this vulnerability.

    Fixed in 1:9.9.5.dfsg-3ubuntu0.19+esm15
  2. Upgrade

    Upgrade ubuntu/bind9 to a version that resolves this vulnerability.

    Fixed in 1:9.10.3.dfsg.P4-8ubuntu1.19+esm11
  3. Upgrade

    Upgrade ubuntu/bind9 to a version that resolves this vulnerability.

    Fixed in 1:9.11.3+dfsg-1ubuntu1.19+esm6
  4. Upgrade

    Upgrade ubuntu/bind9 to a version that resolves this vulnerability.

    Fixed in 1:9.18.30-0ubuntu0.20.04.2+esm3
  5. Upgrade

    Upgrade ubuntu/bind9 to a version that resolves this vulnerability.

    Fixed in 1:9.18.39-0ubuntu0.22.04.7
  6. Upgrade

    Upgrade ubuntu/bind9 to a version that resolves this vulnerability.

    Fixed in 1:9.18.39-0ubuntu0.24.04.8
  7. Upgrade

    Upgrade ubuntu/bind9 to a version that resolves this vulnerability.

    Fixed in 1:9.20.24-1ubuntu3.1
  8. 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·03:17 PM
Data Sourced
via OSV·03:17 PM
DescriptionSeverityAffected Software

Frequently Asked Questions

1

Which deployments are exposed to this issue?

Deployments using affected BIND 9 versions are exposed, including 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.

2

What must an attacker be able to do to exploit it?

An attacker must provide a validly signed NSEC3 record from an unrelated sibling zone that is accepted as an insecurity proof. The attack can downgrade a secure delegation and permit a forged unsigned DNS answer.

3

Does exploitation require credentials or user interaction?

No. The supplied vector identifies network reachability, no privileges, and no user interaction, although it rates attack complexity as high.

Company

Resources

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