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CVE-2026-40211

Status: DeferredMedium (5.3)—

An attacker can send crafted DNS over HTTP/3 queries, triggering an exception that prevents some buffer from being freed right away. The buffer will be freed at the end of the QUIC connection, but on some setups it might be possible to open enough concurrent DoH3 streams to trigger an out-of-memory condition, resulting in a denial of service.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

ISC — BindAI

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2026-40211",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-40211",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-06-25T13:44:56.582604Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security@open-xchange.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "LOW",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security@open-xchange.com",
      "affectedData": [
        {
          "repo": "https://github.com/PowerDNS/pdns",
          "vendor": "PowerDNS",
          "modules": [
            "DNS over HTTP3"
          ],
          "product": "DNSdist",
          "versions": [
            {
              "status": "affected",
              "version": "1.9.0",
              "lessThan": "1.9.15",
              "versionType": "semver"
            },
            {
              "status": "affected",
              "version": "2.0.0",
              "lessThan": "2.0.7",
              "versionType": "semver"
            }
          ],
          "packageName": "dnsdist",
          "programFiles": [
            "dnsdist-crypto.cc"
          ],
          "collectionURL": "https://repo.powerdns.com/",
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-06-25T13:16:39.717",
  "references": [
    {
      "url": "https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html",
      "source": "security@open-xchange.com"
    }
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      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
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  "descriptions": [
    {
      "lang": "en",
      "value": "An attacker can send crafted DNS over HTTP/3 queries, triggering an exception that prevents some buffer from being freed right away. The buffer will be freed at the end of the QUIC connection, but on some setups it might be possible to open enough concurrent DoH3 streams to trigger an out-of-memory condition, resulting in a denial of service."
    }
  ],
  "lastModified": "2026-06-25T15:59:47.100",
  "sourceIdentifier": "security@open-xchange.com"
}