Vulnerability-Lookup

UBUNTU-CVE-2026-42955 (CVE-2026-42955)

Vulnerability from osv_ubuntu – Published: 2026-07-22 14:17 – Updated: 2026-08-20 19:47 – Source website

Details

In NLnet Labs Unbound 1.16.2 up to and including 1.25.1, a similar vulnerability as with CVE-2026-40622 in the 'ghost domain names' family of attacks was found in Unbound that could extend the ghost domain window by up to one cached TTL configured value for A/AAAA glue records. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client A/AAAA query can cause Unbound to overwrite the cached expired parent-side glue rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client query is required since Unbound implicitly performs that query. This is a variant of CVE-2026-40622 which only addressed the NS query.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-42955	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-42955	REPORT
	https://community.nlnetlabs.nl/t/unbound-1-25-2-r…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libunbound2",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
          },
          {
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            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
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          {
            "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"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:14.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.4.22-1ubuntu4.14.04.3+esm3?arch=source\u0026distro=esm-infra-legacy/trusty"
      },
      "ranges": [
        {
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            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
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        "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"
      ]
    },
    {
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            "binary_version": "1.5.8-1ubuntu1.1+esm3"
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            "binary_version": "1.5.8-1ubuntu1.1+esm3"
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          {
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            "binary_version": "1.5.8-1ubuntu1.1+esm3"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
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        "purl": "pkg:deb/ubuntu/unbound@1.5.8-1ubuntu1.1+esm3?arch=source\u0026distro=esm-infra-legacy/xenial"
      },
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    },
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      },
      "ranges": [
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        "1.6.7-1ubuntu2.6+esm3",
        "1.6.7-1ubuntu2.6+esm4"
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    },
    {
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            "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"
          },
          {
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            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          },
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            "binary_name": "unbound-host",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          }
        ]
      },
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        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "unbound",
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      },
      "ranges": [
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        "1.9.0-2ubuntu2",
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        "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",
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      ]
    },
    {
      "ecosystem_specific": {
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          {
            "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"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.13.1-1ubuntu5.15?arch=source\u0026distro=jammy"
      },
      "ranges": [
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            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "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": "1.19.2-1ubuntu3.9"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.19.2-1ubuntu3.9"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.19.2-1ubuntu3.9"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.19.2-1ubuntu3.9"
          },
          {
            "binary_name": "unbound-host",
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      "package": {
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      },
      "ranges": [
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          ],
          "type": "ECOSYSTEM"
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        "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",
        "1.19.2-1ubuntu3.9"
      ]
    },
    {
      "ecosystem_specific": {
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          {
            "binary_name": "libunbound8",
            "binary_version": "1.24.2-1ubuntu2.2"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.24.2-1ubuntu2.2"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.24.2-1ubuntu2.2"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.24.2-1ubuntu2.2"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.24.2-1ubuntu2.2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.24.2-1ubuntu2.2?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
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      ],
      "versions": [
        "1.22.0-2ubuntu2",
        "1.22.0-2ubuntu4",
        "1.24.2-1ubuntu1",
        "1.24.2-1ubuntu2",
        "1.24.2-1ubuntu2.1",
        "1.24.2-1ubuntu2.2"
      ]
    }
  ],
  "aliases": [],
  "details": "In NLnet Labs Unbound 1.16.2 up to and including 1.25.1, a similar vulnerability as with CVE-2026-40622 in the \u0027ghost domain names\u0027 family of attacks was found in Unbound that could extend the ghost domain window by up to one cached TTL configured value for A/AAAA glue records. Similar to other \u0027ghost domain names\u0027 attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client A/AAAA query can cause Unbound to overwrite the cached expired parent-side glue rrset and essentially extend the ghost domain window by up to one cached TTL configured value (\u0027cache-max-ttl\u0027). In configurations where \u0027harden-referral-path: yes\u0027 is used (non-default configuration), no client query is required since Unbound implicitly performs that query. This is a variant of CVE-2026-40622 which only addressed the NS query.",
  "id": "UBUNTU-CVE-2026-42955",
  "modified": "2026-08-20T19:47:18Z",
  "published": "2026-07-22T14:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-42955"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-42955"
    },
    {
      "type": "REPORT",
      "url": "https://community.nlnetlabs.nl/t/unbound-1-25-2-released/3430"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-42955"
  ]
}

CVE-2026-42955 (GCVE-0-2026-42955)

Vulnerability from cvelistv5 – Published: 2026-07-22 13:05 – Updated: 2026-07-22 14:26

Title

Extra fix for CVE-2026-40622 to also clamp the TTL of A/AAAA records disallowing a one-time 'ghost domain' delegation renewal via glue records

Summary

Severity

3.7 (Low)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-22 14:26 UTC

CWE

CWE-672 - Operation on a Resource after Expiration or Release

Assigner

NLnet Labs Scorecard

References

1 reference

URL	Tags
https://www.nlnetlabs.nl/downloads/unbound/CVE-20…	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
NLnet Labs	Unbound	Affected: 1.16.2 , < 1.25.2 (semver)

Date Public

2026-07-22 00:00

Credits

Qifan Zhang (Palo Alto Networks)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-42955",
                "options": [
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                    "Exploitation": "none"
                  },
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                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-22T14:26:22.407643Z",
                "version": "2.0.3"
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              "type": "ssvc"
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          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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          "vendor": "NLnet Labs",
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              "versionType": "semver"
            }
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      "descriptions": [
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          "value": "NLnet Labs shares patch"
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          "time": "2026-06-13T00:00:00.000Z",
          "value": "Qifan Zhang verifies patch"
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          "time": "2026-07-22T00:00:00.000Z",
          "value": "Fixes released with version 1.25.2"
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      ],
      "title": "Extra fix for CVE-2026-40622 to also clamp the TTL of A/AAAA records disallowing a one-time \u0027ghost domain\u0027 delegation renewal via glue records",
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        "engine": "cvelib 1.8.0"
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  "cveMetadata": {
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    "cveId": "CVE-2026-42955",
    "datePublished": "2026-07-22T13:05:53.695Z",
    "dateReserved": "2026-06-22T10:11:10.510Z",
    "dateUpdated": "2026-07-22T14:26:48.806Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Published Proof of Concept: A public proof of concept is available for this vulnerability.
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Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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UBUNTU-CVE-2026-42955 (CVE-2026-42955)

CVE-2026-42955 (GCVE-0-2026-42955)

Tags

Sightings

Nomenclature

Related by attack behaviour