Security advisory

{
  "id": "9758dfe6d5080af5a363b54df71b60f4fa2371e338109687bc7a6d65558d7dc7",
  "url": "https://osv.dev/vulnerability/CVE-2026-32665",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2026-32665",
    "summary": "In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with low-cost input. Using only one connection and two streams, each sending a declared 65535-byte length prefix and then holding the streams open, a client can already trivially make Unbound roughly allocate double that amount. This is a remote availability issue / memory-accounting bypass in the downstream DoQ implementation that leads to denial of service for new DoQ clients. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.",
    "evidence": "osv:CVE-2026-32665",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-32665",
      "aliases": [
        "CVE-2026-32665"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/nlnetlabs/unbound",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0076736fc40298eb6252705e6e158462c6b24d06"
                },
                {
                  "fixed": "c33ad1b1a21e48bfe4f140e90252a9be1b0c5745"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "1.22.0"
                      },
                      {
                        "fixed": "1.25.2"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "release-1.25.1",
            "release-1.25.0",
            "release-1.25.0rc1",
            "release-1.24.0",
            "release-1.24.0rc1",
            "release-1.23.0rc1",
            "release-1.22.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-32665.json"
          }
        }
      ],
      "modified": "2026-10-26T02:30:20.980974327Z",
      "provider": "osv",
      "references": [
        "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-32665.txt"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2026-32665",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 446633,
  "published_at": "2026-07-22T14:17:18.193+00:00"
}