Vulnerability-Lookup

UBUNTU-CVE-2026-33630 (CVE-2026-33630)

Vulnerability from osv_ubuntu – Published: 2026-09-03 19:17 – Updated: 2026-09-16 11:33 – Source website

Details

c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares' query-completion handling. The same flaw — a query's callback being invoked while the query is still linked in the channel's internal lookup structures — is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7.

Severity

7.5 (High)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-33630	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-33630	REPORT
	https://www.openwall.com/lists/oss-security/2026/…	REPORT
	https://github.com/c-ares/c-ares/security/advisor…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libc-ares2",
            "binary_version": "1.10.0-3ubuntu0.2+esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "c-ares",
        "purl": "pkg:deb/ubuntu/c-ares@1.10.0-3ubuntu0.2+esm3?arch=source\u0026distro=esm-infra/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.10.0-2",
        "1.10.0-3",
        "1.10.0-3ubuntu0.1",
        "1.10.0-3ubuntu0.2",
        "1.10.0-3ubuntu0.2+esm1",
        "1.10.0-3ubuntu0.2+esm2",
        "1.10.0-3ubuntu0.2+esm3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libc-ares2",
            "binary_version": "1.14.0-1ubuntu0.2+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "c-ares",
        "purl": "pkg:deb/ubuntu/c-ares@1.14.0-1ubuntu0.2+esm2?arch=source\u0026distro=esm-infra/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.13.0-2",
        "1.13.0-3",
        "1.14.0-1",
        "1.14.0-1ubuntu0.1",
        "1.14.0-1ubuntu0.2",
        "1.14.0-1ubuntu0.2+esm1",
        "1.14.0-1ubuntu0.2+esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libc-ares2",
            "binary_version": "1.15.0-1ubuntu0.5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "c-ares",
        "purl": "pkg:deb/ubuntu/c-ares@1.15.0-1ubuntu0.5?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.15.0-1build1",
        "1.15.0-1ubuntu0.1",
        "1.15.0-1ubuntu0.2",
        "1.15.0-1ubuntu0.3",
        "1.15.0-1ubuntu0.4",
        "1.15.0-1ubuntu0.5"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libc-ares2",
            "binary_version": "1.18.1-1ubuntu0.22.04.3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "c-ares",
        "purl": "pkg:deb/ubuntu/c-ares@1.18.1-1ubuntu0.22.04.3?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.17.1-1ubuntu1",
        "1.18.1-1",
        "1.18.1-1build1",
        "1.18.1-1ubuntu0.22.04.1",
        "1.18.1-1ubuntu0.22.04.2",
        "1.18.1-1ubuntu0.22.04.3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libcares2",
            "binary_version": "1.27.0-1.0ubuntu1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "c-ares",
        "purl": "pkg:deb/ubuntu/c-ares@1.27.0-1.0ubuntu1?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.19.1-3",
        "1.20.1-1",
        "1.26.0-1",
        "1.27.0-1",
        "1.27.0-1.0ubuntu1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libc-ares2",
            "binary_version": "1.34.5-1ubuntu0.1"
          },
          {
            "binary_name": "libcares2",
            "binary_version": "1.34.5-1ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "c-ares",
        "purl": "pkg:deb/ubuntu/c-ares@1.34.5-1ubuntu0.1?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.34.4-2.1",
        "1.34.5-1",
        "1.34.5-1ubuntu0.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libc-ares2",
            "binary_version": "1.34.6-1"
          },
          {
            "binary_name": "libcares2",
            "binary_version": "1.34.6-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "c-ares",
        "purl": "pkg:deb/ubuntu/c-ares@1.34.6-1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.34.5-1",
        "1.34.6-1"
      ]
    }
  ],
  "aliases": [],
  "details": "c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares\u0027 query-completion handling. The same flaw \u2014 a query\u0027s callback being invoked while the query is still linked in the channel\u0027s internal lookup structures \u2014 is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7.",
  "id": "UBUNTU-CVE-2026-33630",
  "modified": "2026-09-16T11:33:17Z",
  "published": "2026-09-03T19:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-33630"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-33630"
    },
    {
      "type": "REPORT",
      "url": "https://www.openwall.com/lists/oss-security/2026/07/06/8"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/c-ares/c-ares/security/advisories/GHSA-6wfj-rwm7-3542"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-33630"
  ]
}

CVE-2026-33630 (GCVE-0-2026-33630)

Vulnerability from cvelistv5 – Published: 2026-09-03 18:42 – Updated: 2026-09-05 02:00

Title

c-ares : Use-after-free / double-free in c-ares query-completion handling, remotely triggerable via ares_getaddrinfo() over TCP

Summary

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-05 02:00 UTC

CWE

CWE-415 - Double Free
CWE-416 - Use After Free

Assigner

GitHub_M mitre root

References

5 references

URL	Tags
https://github.com/c-ares/c-ares/security/advisor…	x_refsource_CONFIRM
https://github.com/c-ares/c-ares/pull/1237	x_refsource_MISC
https://github.com/c-ares/c-ares/commit/1fa3b86a0…	x_refsource_MISC
https://github.com/c-ares/c-ares/commit/d823199b6…	x_refsource_MISC
https://github.com/c-ares/c-ares/releases/tag/v1.34.7	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
c-ares	c-ares	Affected: >= 1.32.3, < 1.34.7

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-33630",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-05T02:00:43.010024Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-05T02:00:52.338Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "c-ares",
          "vendor": "c-ares",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 1.32.3, \u003c 1.34.7"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares\u0027 query-completion handling. The same flaw \u2014 a query\u0027s callback being invoked while the query is still linked in the channel\u0027s internal lookup structures \u2014 is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-415",
              "description": "CWE-415: Double Free",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-416",
              "description": "CWE-416: Use After Free",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-03T20:04:36.574Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/c-ares/c-ares/security/advisories/GHSA-6wfj-rwm7-3542",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/c-ares/c-ares/security/advisories/GHSA-6wfj-rwm7-3542"
        },
        {
          "name": "https://github.com/c-ares/c-ares/pull/1237",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/c-ares/c-ares/pull/1237"
        },
        {
          "name": "https://github.com/c-ares/c-ares/commit/1fa3b86a0b8d18fe7b60f3228a01d770feb026bc",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/c-ares/c-ares/commit/1fa3b86a0b8d18fe7b60f3228a01d770feb026bc"
        },
        {
          "name": "https://github.com/c-ares/c-ares/commit/d823199b688052dcdc1646f2ab4cb8c16b1c644a",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/c-ares/c-ares/commit/d823199b688052dcdc1646f2ab4cb8c16b1c644a"
        },
        {
          "name": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7"
        }
      ],
      "source": {
        "advisory": "GHSA-6wfj-rwm7-3542",
        "discovery": "UNKNOWN"
      },
      "title": "c-ares : Use-after-free / double-free in c-ares query-completion handling, remotely triggerable via ares_getaddrinfo() over TCP"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-33630",
    "datePublished": "2026-09-03T18:42:28.783Z",
    "dateReserved": "2026-03-23T14:24:11.618Z",
    "dateUpdated": "2026-09-05T02:00:52.338Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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}

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.
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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.