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[USN-8282-2] Unbound vulnerabilities

Posted on 02 June 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8282-2
June 02, 2026

unbound vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

Several security issues were fixed in Unbound.

Software Description:
- unbound: validating, recursive, caching DNS resolver

Details:

USN-8282-1 fixed vulnerabilities in Unbound. This update provides the
corresponding updates for CVE-2026-41292 in Ubuntu 18.04 LTS and Ubuntu
20.04 LTS and CVE-2026-42959, CVE-2026-42960 in Ubuntu 14.04 LTS, Ubuntu
16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS.

Original advisory details:

Andrew Griffiths discovered that Unbound did not properly handle certain
DNSCrypt packets. A remote attacker could possibly use this issue to cause
Unbound to crash, resulting in a denial of service. (CVE-2026-32792)

Qifan Zhang discovered that Unbound incorrectly handled DNSSEC validation
in certain situations. A remote attacker could possibly use this issue to
execute arbitrary code. This issue only affected Ubuntu 24.04 LTS, Ubuntu
25.10, and Ubuntu 26.04 LTS. (CVE-2026-33278)

Qifan Zhang discovered that Unbound incorrectly handled certain ghost
domain name records. A remote attacker could possibly use this issue to
cause a denial of service. This issue only affected Ubuntu 24.04 LTS,
Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-40622)

Qifan Zhang discovered that Unbound did not properly limit processing of
long EDNS option lists. A remote attacker could possibly use this issue to
cause Unbound to use excessive resources, leading to a denial of service.
(CVE-2026-41292)

Qifan Zhang discovered that Unbound incorrectly handled jostle logic under
certain circumstances. A remote attacker could possibly use this issue to
cause Unbound to use excessive resources, leading to a denial of service.
(CVE-2026-42534)

Qifan Zhang discovered that Unbound did not properly bound NSEC3 hash
calculations. A remote attacker could possibly use this issue to cause
Unbound to use excessive resources, leading to a denial of service.
(CVE-2026-42923)

Qifan Zhang discovered that Unbound incorrectly handled multiple EDNS
options in certain situations. A remote attacker could possibly use this
issue to cause Unbound to crash, resulting in a denial of service, or
execute arbitrary code. This issue only affected Ubuntu 24.04 LTS, Ubuntu
25.10, and Ubuntu 26.04 LTS. (CVE-2026-42944)

Qifan Zhang discovered that Unbound incorrectly handled DNSSEC validation
of malicious content. A remote attacker could possibly use this issue to
cause Unbound to crash, resulting in a denial of service.
(CVE-2026-42959)

TaoFei Guo, Yang Luo, and JianJun Chen discovered that Unbound
incorrectly handled delegation processing in certain situations. A remote
attacker could possibly use this issue to poison the DNS cache and obtain
sensitive information. (CVE-2026-42960)

Qifan Zhang discovered that Unbound did not properly bound name
compression in certain cases. A remote attacker could possibly use this
issue to cause Unbound to use excessive resources, leading to a denial of
service. (CVE-2026-44390)

Qifan Zhang discovered that Unbound had a use-after-free issue in RPZ
handling. A remote attacker could possibly use this issue to cause Unbound
to crash, resulting in a denial of service, or execute arbitrary code.
This issue only affected Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04
LTS. (CVE-2026-44608)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 20.04 LTS
libunbound8 1.9.4-2ubuntu1.11+esm1
Available with Ubuntu Pro
unbound 1.9.4-2ubuntu1.11+esm1
Available with Ubuntu Pro

Ubuntu 18.04 LTS
libunbound2 1.6.7-1ubuntu2.6+esm4
Available with Ubuntu Pro
unbound 1.6.7-1ubuntu2.6+esm4
Available with Ubuntu Pro

Ubuntu 16.04 LTS
libunbound2 1.5.8-1ubuntu1.1+esm3
Available with Ubuntu Pro
unbound 1.5.8-1ubuntu1.1+esm3
Available with Ubuntu Pro

Ubuntu 14.04 LTS
libunbound2 1.4.22-1ubuntu4.14.04.3+esm3
Available with Ubuntu Pro
unbound 1.4.22-1ubuntu4.14.04.3+esm3
Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8282-2
https://ubuntu.com/security/notices/USN-8282-1
CVE-2026-41292, CVE-2026-42959, CVE-2026-42960

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