{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "1.10.0"
              },
              {
                "fixed": "1.25.2"
              }
            ],
            "source": "CPE_RANGE"
          },
          "events": [
            {
              "introduced": "6e7717986b25a48952ebb18e131d6eaa005a9757"
            },
            {
              "fixed": "c33ad1b1a21e48bfe4f140e90252a9be1b0c5745"
            }
          ],
          "repo": "https://github.com/nlnetlabs/unbound",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {},
  "details": "In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a 'response-ip: \u003cnet\u003e redirect' /'response-ip-data: \u003cnet\u003e CNAME \u003ctarget\u003e' rule (or the RPZ 'rpz-cname-override' equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets 'alias_rrset' but not 'partial_rep'. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-timeout' is taken leading to denial of service via the server crash.",
  "id": "CVE-2026-55717",
  "modified": "2026-07-27T11:42:29.589331956Z",
  "published": "2026-07-22T14:17:21.537Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-55717.txt"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}