Vulnerability-Lookup

ubuntu-cve-2026-56416

Vulnerability from osv_ubuntu

Published

2026-07-22 14:17

Modified

2026-07-29 07:59

Summary

Details

In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as 'datstart + dname_valid(datstart, ...)' and passes it straight to 'query_dname_tolower()' without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause 'query_dname_tolower()' to walk label-by-label through stale bytes in the per-worker 'env->scratch_buffer', past the end of that heap allocation if 'msg-buffer-size' has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.

Severity

4.8 (Medium)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-56416	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-56416	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"
          },
          {
            "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"
          }
        ]
      },
      "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": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "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": "1.5.8-1ubuntu1.1+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"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.5.8-1ubuntu1.1+esm3?arch=source\u0026distro=esm-infra-legacy/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "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": "1.6.7-1ubuntu2.6+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"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.6.7-1ubuntu2.6+esm4?arch=source\u0026distro=esm-infra/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "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": "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"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.9.4-2ubuntu1.11+esm1?arch=source\u0026distro=esm-infra/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "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": "1.13.1-1ubuntu5.15"
          },
          {
            "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": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "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": "1.19.2-1ubuntu3.8"
          },
          {
            "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"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.19.2-1ubuntu3.8?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "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": "1.24.2-1ubuntu2.1"
          },
          {
            "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"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.24.2-1ubuntu2.1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.22.0-2ubuntu2",
        "1.22.0-2ubuntu4",
        "1.24.2-1ubuntu1",
        "1.24.2-1ubuntu2",
        "1.24.2-1ubuntu2.1"
      ]
    }
  ],
  "aliases": [],
  "details": "In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as \u0027datstart + dname_valid(datstart, ...)\u0027 and passes it straight to \u0027query_dname_tolower()\u0027 without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause \u0027query_dname_tolower()\u0027 to walk label-by-label through stale bytes in the per-worker \u0027env-\u003escratch_buffer\u0027, past the end of that heap allocation if \u0027msg-buffer-size\u0027 has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.",
  "id": "UBUNTU-CVE-2026-56416",
  "modified": "2026-07-29T07:59:16Z",
  "published": "2026-07-22T14:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-56416"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-56416"
    },
    {
      "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:L",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-56416"
  ]
}

CVE-2026-56416 (GCVE-0-2026-56416)

Vulnerability from cvelistv5 – Published: 2026-07-22 13:10 – Updated: 2026-07-22 14:00

Title

Possible heap buffer overflow when validator canonicalizes RDATA that contains domain name

Summary

Severity

4.8 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-354 - Improper Validation of Integrity Check Value

Assigner

NLnet Labs

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: 0 , < 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-2026-56416",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-22T13:59:48.705600Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
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        "providerMetadata": {
          "dateUpdated": "2026-07-22T14:00:45.744Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
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          "product": "Unbound",
          "vendor": "NLnet Labs",
          "versions": [
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              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
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        }
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      "descriptions": [
        {
          "lang": "en",
          "value": "In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as \u0027datstart + dname_valid(datstart, ...)\u0027 and passes it straight to \u0027query_dname_tolower()\u0027 without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause \u0027query_dname_tolower()\u0027 to walk label-by-label through stale bytes in the per-worker \u0027env-\u003escratch_buffer\u0027, past the end of that heap allocation if \u0027msg-buffer-size\u0027 has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk."
        }
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              "description": "CWE-354: Improper Validation of Integrity Check Value",
              "lang": "en",
              "type": "CWE"
            }
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      "providerMetadata": {
        "dateUpdated": "2026-07-22T13:10:24.023Z",
        "orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6",
        "shortName": "NLnet Labs"
      },
      "references": [
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          "tags": [
            "vendor-advisory"
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        }
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      "solutions": [
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          "value": "This issue is fixed starting with version 1.25.2"
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          "value": "Issue reported by Qifan Zhang"
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          "lang": "en",
          "time": "2026-05-29T00:00:00.000Z",
          "value": "NLnet Labs shares patch"
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        {
          "lang": "en",
          "time": "2026-06-03T00:00:00.000Z",
          "value": "Qifan Zhang verifies patch"
        },
        {
          "lang": "en",
          "time": "2026-07-22T00:00:00.000Z",
          "value": "Fixes released with version 1.25.2"
        }
      ],
      "title": "Possible heap buffer overflow when validator canonicalizes RDATA that contains domain name",
      "x_generator": {
        "engine": "cvelib 1.8.0"
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  },
  "cveMetadata": {
    "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6",
    "assignerShortName": "NLnet Labs",
    "cveId": "CVE-2026-56416",
    "datePublished": "2026-07-22T13:10:24.023Z",
    "dateReserved": "2026-06-22T12:27:22.810Z",
    "dateUpdated": "2026-07-22T14:00:45.744Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

ubuntu-cve-2026-56416

Vulnerability from osv_ubuntu

CVE-2026-56416 (GCVE-0-2026-56416)

Tags

Sightings

Nomenclature