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

Vulnerability from osv_ubuntu – Published: 2026-09-03 19:17 – Updated: 2026-09-29 20:26 – Source website
VLAI
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
To clipboard 

{
  "affected": [
    {
      "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": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libc-ares2",
            "binary_version": "1.34.6-1ubuntu0.1"
          },
          {
            "binary_name": "libcares2",
            "binary_version": "1.34.6-1ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "c-ares",
        "purl": "pkg:deb/ubuntu/c-ares@1.34.6-1ubuntu0.1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.34.6-1ubuntu0.1"
            }
          ],
          "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": "2026-09-29T20:26:39Z",
  "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"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8844-1"
    }
  ],
  "related": [
    "USN-8844-1"
  ],
  "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"
  ]
}



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