{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "1.22.0"
              },
              {
                "fixed": "1.25.2"
              }
            ],
            "source": "CPE_RANGE"
          },
          "events": [
            {
              "introduced": "0076736fc40298eb6252705e6e158462c6b24d06"
            },
            {
              "fixed": "c33ad1b1a21e48bfe4f140e90252a9be1b0c5745"
            }
          ],
          "repo": "https://github.com/nlnetlabs/unbound",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {},
  "details": "In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, client terminated DNS-over-QUIC (DoQ) queries are not accounted properly by Unbound resulting in low-cost inflation of the waiting number of replies for already in-flight resolution queries. This results in degradation of resolution service for new clients for already in-flight queries. A malicious actor can exploit the vulnerability by issuing DoQ queries for query names that need resolution and proceeding on immediately terminating the query by one of STOP_SENDING/RESET_STREAM/CONNECTION_CLOSE QUIC frames. Those terminated DoQ queries are not properly counted for and keep inflating the number of waiting replies for in-flight queries. When the maximum is reached, it results in silent query drops for new clients needing resolution for already in-flight queries. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces. Additionally, a malicious actor needs access to multiple source IPs to bypass the by-default configured 'wait-limit' option.",
  "id": "CVE-2026-41637",
  "modified": "2026-07-27T11:42:21.057419113Z",
  "published": "2026-07-22T14:17:18.560Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-41637.txt"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ]
}