UBUNTU-CVE-2026-55717

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Source
https://ubuntu.com/security/CVE-2026-55717
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55717.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-55717
Upstream
Published
2026-07-22T14:17:00Z
Modified
2026-07-29T10:16:07.882063639Z
Severity
  • 5.9 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a 'response-ip: <net> redirect' /'response-ip-data: <net> CNAME <target>' rule (or the RPZ 'rpz-cname-override' equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets 'aliasrrset' but not 'partialrep'. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-timeout' is taken leading to denial of service via the server crash.

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

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
1.13.1-1ubuntu5.15

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.13.1-1ubuntu5.15",
            "binary_name": "libunbound8"
        },
        {
            "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-2026-55717.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

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
1.19.2-1ubuntu3.8

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.19.2-1ubuntu3.8",
            "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_name": "unbound-host"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55717.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

Affected versions

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

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.24.2-1ubuntu2.1",
            "binary_name": "libunbound8"
        },
        {
            "binary_version": "1.24.2-1ubuntu2.1",
            "binary_name": "python3-unbound"
        },
        {
            "binary_version": "1.24.2-1ubuntu2.1",
            "binary_name": "unbound"
        },
        {
            "binary_version": "1.24.2-1ubuntu2.1",
            "binary_name": "unbound-anchor"
        },
        {
            "binary_version": "1.24.2-1ubuntu2.1",
            "binary_name": "unbound-host"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55717.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

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
1.4.22-1ubuntu4.14.04.3+esm3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3",
            "binary_name": "libunbound2"
        },
        {
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3",
            "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"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55717.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

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
1.5.8-1ubuntu1.1+esm3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.5.8-1ubuntu1.1+esm3",
            "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_name": "unbound-anchor"
        },
        {
            "binary_version": "1.5.8-1ubuntu1.1+esm3",
            "binary_name": "unbound-host"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55717.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

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
1.6.7-1ubuntu2.6+esm4

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.6.7-1ubuntu2.6+esm4",
            "binary_name": "libunbound2"
        },
        {
            "binary_version": "1.6.7-1ubuntu2.6+esm4",
            "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_name": "unbound-host"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55717.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

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
1.9.4-2ubuntu1.11+esm1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.9.4-2ubuntu1.11+esm1",
            "binary_name": "libunbound8"
        },
        {
            "binary_version": "1.9.4-2ubuntu1.11+esm1",
            "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"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55717.json"