UBUNTU-CVE-2026-50252

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Source

https://ubuntu.com/security/CVE-2026-50252

Import Source

https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50252.json

JSON Data

https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-50252

Upstream

CVE-2026-50252

Published

2026-07-22T14:17:00Z

Modified

2026-07-29T10:16:01.073964507Z

Severity

5.7 (Medium) CVSS_V4 - CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P/U:Amber CVSS Calculator
9.3 (Critical) CVSS_V3 - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H CVSS Calculator
Ubuntu - medium

Summary

[none]

Details

In NLnet Labs Unbound 1.4.22 up to and including 1.25.1, UDP source port is randomized and intended to serve as a secret value that increases the entropy of DNS transactions. When resolver load balancing policies depend on the source port while their outcome is revealed this secrecy is undermined. The vulnerability arises when the load balancing policy is consistent with respect to the incoming source UDP port and IP address while heavily depending on the incoming source UDP port as a randomization source. When the SOREUSEPORT configuration option is enabled ('so-reuseport: yes') in Unbound (by default), it meets these conditions, making it vulnerable for DNS cache poisoning attacks. Upon startup, Unbound randomly partitions the available UDP source port space into disjoint subsets of (almost) equal size, assigning each subset to a specific worker thread. When an incoming DNS query is received, the kernel’s SOREUSEPORT load balancing mechanism deterministically assigns the query to a socket associated with a particular thread. All outgoing DNS queries generated during the resolution of that request use source ports selected exclusively from the port subset assigned to the corresponding thread. Since these port subsets are disjoint across threads, the source port observed in a resolver’s outgoing query to an authoritative name server serves as a reliable indicator of the worker thread that processed the original client query. A malicious actor can acquire the mapping between incoming UDP source ports (for a given fixed source IP address) and Unbound worker threads and leverage it to conduct DNS cache poisoning attacks by effectively lowering the random port population per thread.

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_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",
            "binary_version": "1.13.1-1ubuntu5.15"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50252.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_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",
            "binary_version": "1.19.2-1ubuntu3.8"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50252.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_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",
            "binary_version": "1.24.2-1ubuntu2.1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50252.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_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",
            "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-2026-50252.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_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",
            "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-2026-50252.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_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",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-50252.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_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",
            "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-2026-50252.json"