UBUNTU-CVE-2026-42959

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Source
https://ubuntu.com/security/CVE-2026-42959
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json
JSON Data
https://api.test.osv.dev/v1/vulns/UBUNTU-CVE-2026-42959
Upstream
Downstream
Related
Published
2026-05-20T00:00:00Z
Modified
2026-06-02T20:29:12.240504444Z
Severity
  • 8.7 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/U:Red CVSS Calculator
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.

References

Affected packages

Ubuntu:22.04:LTS
unbound

Package

Name
unbound
Purl
pkg:deb/ubuntu/unbound?arch=source&distro=jammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.13.1-1ubuntu5.15

Affected versions

1.*
1.13.1-1ubuntu1
1.13.1-1ubuntu3
1.13.1-1ubuntu5
1.13.1-1ubuntu5.1
1.13.1-1ubuntu5.2
1.13.1-1ubuntu5.3
1.13.1-1ubuntu5.4
1.13.1-1ubuntu5.5
1.13.1-1ubuntu5.7
1.13.1-1ubuntu5.8
1.13.1-1ubuntu5.10
1.13.1-1ubuntu5.11
1.13.1-1ubuntu5.12
1.13.1-1ubuntu5.13
1.13.1-1ubuntu5.14

Ecosystem specific 

{
    "availability": "No subscription required",
    "binaries": [
        {
            "binary_name": "libunbound8",
            "binary_version": "1.13.1-1ubuntu5.15"
        },
        {
            "binary_version": "1.13.1-1ubuntu5.15",
            "binary_name": "python3-unbound"
        },
        {
            "binary_version": "1.13.1-1ubuntu5.15",
            "binary_name": "unbound"
        },
        {
            "binary_version": "1.13.1-1ubuntu5.15",
            "binary_name": "unbound-anchor"
        },
        {
            "binary_version": "1.13.1-1ubuntu5.15",
            "binary_name": "unbound-host"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json"
Ubuntu:24.04:LTS
unbound

Package

Name
unbound
Purl
pkg:deb/ubuntu/unbound?arch=source&distro=noble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.19.2-1ubuntu3.8

Affected versions

1.*
1.17.1-2
1.18.0-2ubuntu1
1.18.0-2ubuntu2
1.19.1-1ubuntu1
1.19.2-1ubuntu1
1.19.2-1ubuntu3
1.19.2-1ubuntu3.1
1.19.2-1ubuntu3.2
1.19.2-1ubuntu3.3
1.19.2-1ubuntu3.4
1.19.2-1ubuntu3.5
1.19.2-1ubuntu3.6
1.19.2-1ubuntu3.7

Ecosystem specific 

{
    "availability": "No subscription required",
    "binaries": [
        {
            "binary_name": "libunbound8",
            "binary_version": "1.19.2-1ubuntu3.8"
        },
        {
            "binary_name": "python3-unbound",
            "binary_version": "1.19.2-1ubuntu3.8"
        },
        {
            "binary_name": "unbound",
            "binary_version": "1.19.2-1ubuntu3.8"
        },
        {
            "binary_name": "unbound-anchor",
            "binary_version": "1.19.2-1ubuntu3.8"
        },
        {
            "binary_version": "1.19.2-1ubuntu3.8",
            "binary_name": "unbound-host"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json"
Ubuntu:25.10
unbound

Package

Name
unbound
Purl
pkg:deb/ubuntu/unbound?arch=source&distro=questing

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.22.0-2ubuntu2.3

Affected versions

1.*
1.22.0-1ubuntu1
1.22.0-2ubuntu1
1.22.0-2ubuntu2
1.22.0-2ubuntu2.1
1.22.0-2ubuntu2.2

Ecosystem specific 

{
    "availability": "No subscription required",
    "binaries": [
        {
            "binary_version": "1.22.0-2ubuntu2.3",
            "binary_name": "libunbound8"
        },
        {
            "binary_version": "1.22.0-2ubuntu2.3",
            "binary_name": "python3-unbound"
        },
        {
            "binary_name": "unbound",
            "binary_version": "1.22.0-2ubuntu2.3"
        },
        {
            "binary_version": "1.22.0-2ubuntu2.3",
            "binary_name": "unbound-anchor"
        },
        {
            "binary_name": "unbound-host",
            "binary_version": "1.22.0-2ubuntu2.3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json"
Ubuntu:26.04:LTS
unbound

Package

Name
unbound
Purl
pkg:deb/ubuntu/unbound?arch=source&distro=resolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.24.2-1ubuntu2.1

Affected versions

1.*
1.22.0-2ubuntu2
1.22.0-2ubuntu4
1.24.2-1ubuntu1
1.24.2-1ubuntu2

Ecosystem specific 

{
    "availability": "No subscription required",
    "binaries": [
        {
            "binary_version": "1.24.2-1ubuntu2.1",
            "binary_name": "libunbound8"
        },
        {
            "binary_name": "python3-unbound",
            "binary_version": "1.24.2-1ubuntu2.1"
        },
        {
            "binary_version": "1.24.2-1ubuntu2.1",
            "binary_name": "unbound"
        },
        {
            "binary_name": "unbound-anchor",
            "binary_version": "1.24.2-1ubuntu2.1"
        },
        {
            "binary_name": "unbound-host",
            "binary_version": "1.24.2-1ubuntu2.1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json"
Ubuntu:Pro:14.04:LTS
unbound

Package

Name
unbound
Purl
pkg:deb/ubuntu/unbound?arch=source&distro=esm-infra-legacy%2Ftrusty

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.4.22-1ubuntu4.14.04.3+esm3

Affected versions

1.*
1.4.20-1
1.4.21-1
1.4.21-1ubuntu1
1.4.21-1ubuntu2
1.4.22-1ubuntu1
1.4.22-1ubuntu2
1.4.22-1ubuntu3
1.4.22-1ubuntu4
1.4.22-1ubuntu4.14.04.1
1.4.22-1ubuntu4.14.04.2
1.4.22-1ubuntu4.14.04.3
1.4.22-1ubuntu4.14.04.3+esm1
1.4.22-1ubuntu4.14.04.3+esm2

Ecosystem specific 

{
    "availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro",
    "binaries": [
        {
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3",
            "binary_name": "libunbound2"
        },
        {
            "binary_name": "python-unbound",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
        },
        {
            "binary_name": "unbound",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
        },
        {
            "binary_name": "unbound-anchor",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
        },
        {
            "binary_name": "unbound-host",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json"
Ubuntu:Pro:16.04:LTS
unbound

Package

Name
unbound
Purl
pkg:deb/ubuntu/unbound?arch=source&distro=esm-infra-legacy%2Fxenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.5.8-1ubuntu1.1+esm3

Affected versions

1.*
1.4.22-1ubuntu6
1.5.7-1ubuntu1
1.5.7-1ubuntu2
1.5.8-1ubuntu1
1.5.8-1ubuntu1.1
1.5.8-1ubuntu1.1+esm1
1.5.8-1ubuntu1.1+esm2

Ecosystem specific 

{
    "availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro",
    "binaries": [
        {
            "binary_name": "libunbound2",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
        },
        {
            "binary_name": "python-unbound",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
        },
        {
            "binary_name": "unbound",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
        },
        {
            "binary_version": "1.5.8-1ubuntu1.1+esm3",
            "binary_name": "unbound-anchor"
        },
        {
            "binary_name": "unbound-host",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json"
Ubuntu:Pro:18.04:LTS
unbound

Package

Name
unbound
Purl
pkg:deb/ubuntu/unbound?arch=source&distro=esm-infra%2Fbionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.6.7-1ubuntu2.6+esm4

Affected versions

1.*
1.6.5-1
1.6.7-1
1.6.7-1build1
1.6.7-1ubuntu1
1.6.7-1ubuntu2
1.6.7-1ubuntu2.1
1.6.7-1ubuntu2.2
1.6.7-1ubuntu2.3
1.6.7-1ubuntu2.4
1.6.7-1ubuntu2.5
1.6.7-1ubuntu2.6
1.6.7-1ubuntu2.6+esm2
1.6.7-1ubuntu2.6+esm3

Ecosystem specific 

{
    "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
    "binaries": [
        {
            "binary_version": "1.6.7-1ubuntu2.6+esm4",
            "binary_name": "libunbound2"
        },
        {
            "binary_name": "python-unbound",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
        },
        {
            "binary_name": "python3-unbound",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
        },
        {
            "binary_name": "unbound",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
        },
        {
            "binary_name": "unbound-anchor",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
        },
        {
            "binary_version": "1.6.7-1ubuntu2.6+esm4",
            "binary_name": "unbound-host"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json"
Ubuntu:Pro:20.04:LTS
unbound

Package

Name
unbound
Purl
pkg:deb/ubuntu/unbound?arch=source&distro=esm-infra%2Ffocal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.9.4-2ubuntu1.11+esm1

Affected versions

1.*
1.9.0-2ubuntu1
1.9.0-2ubuntu2
1.9.4-2
1.9.4-2ubuntu1
1.9.4-2ubuntu1.1
1.9.4-2ubuntu1.2
1.9.4-2ubuntu1.3
1.9.4-2ubuntu1.4
1.9.4-2ubuntu1.5
1.9.4-2ubuntu1.6
1.9.4-2ubuntu1.8
1.9.4-2ubuntu1.9
1.9.4-2ubuntu1.11

Ecosystem specific 

{
    "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
    "binaries": [
        {
            "binary_version": "1.9.4-2ubuntu1.11+esm1",
            "binary_name": "libunbound8"
        },
        {
            "binary_name": "python-unbound",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
        },
        {
            "binary_name": "python3-unbound",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
        },
        {
            "binary_name": "unbound",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
        },
        {
            "binary_name": "unbound-anchor",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
        },
        {
            "binary_name": "unbound-host",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42959.json"