unbound security update

{
  "id": "4d58596e8b3c01c54cc69d945b9229a08aa9c9e128e4c0ecc452a590f4a76ca8",
  "url": "https://osv.dev/vulnerability/OESA-2026-4276",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "unbound security update",
    "summary": "Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only. Security Fix(es): In NLnetLabs Unbound 1.20.0 up to and including 1.26.0, a vulnerability on the 'serve-expired' code path can cause a double decrement on the 'wait-limit' counter per client IP essentially bypassing one of the counter measures that was introduced for DNSBomb (CVE-2024-33655). A malicious actor can exploit this by controlling an authoritative zone with short TTL, so cached entries expire quickly. Each 'slow' query, one the attacker's authoritative never answers, is followed by one query for an expired cached name, which is answered immediately via the 'serve-expired' path and decrements the counter twice. This second query was named 'pump'. By alternating slow queries and pumps, the attacker keeps the per-client counter at or below the configured 'wait-limit' indefinitely, and can hold an arbitrary number of pending queries from a single source IP, up to the global mesh quota (num-queries-per-thread); eventually bypassing one of the",
    "evidence": "osv:OESA-2026-4276",
    "products": [
      {
        "name": {
          "value": "unbound",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.13.2-29.oe2203sp4",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "OESA-2026-4276",
      "aliases": [
        "OESA-2026-4276"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1.13.2-29.oe2203sp4"
                }
              ]
            }
          ],
          "package": {
            "name": "unbound",
            "purl": "pkg:rpm/openEuler/unbound&distro=openEuler-22.03-LTS-SP4",
            "ecosystem": "openEuler:22.03-LTS-SP4"
          },
          "database_specific": {
            "source": "https://repo.openeuler.org/security/data/osv/OESA-2026-4276.json"
          },
          "ecosystem_specific": {
            "src": [
              "unbound-1.13.2-29.oe2203sp4.src.rpm"
            ],
            "x86_64": [
              "python3-unbound-1.13.2-29.oe2203sp4.x86_64.rpm",
              "unbound-1.13.2-29.oe2203sp4.x86_64.rpm",
              "unbound-anchor-1.13.2-29.oe2203sp4.x86_64.rpm",
              "unbound-debuginfo-1.13.2-29.oe2203sp4.x86_64.rpm",
              "unbound-debugsource-1.13.2-29.oe2203sp4.x86_64.rpm",
              "unbound-devel-1.13.2-29.oe2203sp4.x86_64.rpm",
              "unbound-help-1.13.2-29.oe2203sp4.x86_64.rpm",
              "unbound-libs-1.13.2-29.oe2203sp4.x86_64.rpm"
            ],
            "aarch64": [
              "python3-unbound-1.13.2-29.oe2203sp4.aarch64.rpm",
              "unbound-1.13.2-29.oe2203sp4.aarch64.rpm",
              "unbound-anchor-1.13.2-29.oe2203sp4.aarch64.rpm",
              "unbound-debuginfo-1.13.2-29.oe2203sp4.aarch64.rpm",
              "unbound-debugsource-1.13.2-29.oe2203sp4.aarch64.rpm",
              "unbound-devel-1.13.2-29.oe2203sp4.aarch64.rpm",
              "unbound-help-1.13.2-29.oe2203sp4.aarch64.rpm",
              "unbound-libs-1.13.2-29.oe2203sp4.aarch64.rpm"
            ]
          }
        }
      ],
      "modified": "2026-10-16T12:15:17.570837722Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-77860",
        "CVE-2026-77955",
        "CVE-2026-82720",
        "CVE-2026-85501"
      ],
      "references": [
        "https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-4276",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-77860",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-77955",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-82720",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-85501"
      ],
      "provider_metadata": {
        "severity": "Medium"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-77860",
        "evidence": "/upstream"
      },
      {
        "value": "CVE-2026-77955",
        "evidence": "/upstream"
      },
      {
        "value": "CVE-2026-82720",
        "evidence": "/upstream"
      },
      {
        "value": "CVE-2026-85501",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 340878,
  "published_at": "2026-10-16T11:58:51+00:00"
}