CVE-2026-40209 (GCVE-0-2026-40209)

Vulnerability from cvelistv5 – Published: 2026-06-25 12:23 – Updated: 2026-06-25 13:56
VLAI
Title
Denial of service via IXFR queries
Summary
An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-25 13:56 UTC
CWE
  • Missing Release of Resource after Effective Lifetime
  • CWE-772 - Missing Release of Resource after Effective Lifetime
Assigner
References
Impacted products
Vendor Product Version CPE status
PowerDNS DNSdist Affected: 1.9.0 , < 1.9.15 (semver)
Affected: 2.0.0 , < 2.0.7 (semver)
guessed Create a notification for this product.
Date Public
2026-06-24 22:00
Credits
Qifan Zhang (Palo Alto Networks)
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-40209",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-25T13:56:17.791790Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-772",
                "description": "CWE-772 Missing Release of Resource after Effective Lifetime",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-25T13:56:22.793Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://repo.powerdns.com/",
          "defaultStatus": "unaffected",
          "modules": [
            "DNS over TCP to the backend"
          ],
          "packageName": "dnsdist",
          "product": "DNSdist",
          "programFiles": [
            "dnsdist-tcp-downstream.cc"
          ],
          "repo": "https://github.com/PowerDNS/pdns",
          "vendor": "PowerDNS",
          "versions": [
            {
              "lessThan": "1.9.15",
              "status": "affected",
              "version": "1.9.0",
              "versionType": "semver"
            },
            {
              "lessThan": "2.0.7",
              "status": "affected",
              "version": "2.0.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Qifan Zhang (Palo Alto Networks)"
        }
      ],
      "datePublic": "2026-06-24T22:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eAn attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors.\u003c/p\u003e"
            }
          ],
          "value": "An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "Missing Release of Resource after Effective Lifetime",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-25T12:23:05.694Z",
        "orgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981",
        "shortName": "OX"
      },
      "references": [
        {
          "url": "https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Denial of service via IXFR queries",
      "x_generator": {
        "engine": "Vulnogram 1.0.2"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981",
    "assignerShortName": "OX",
    "cveId": "CVE-2026-40209",
    "datePublished": "2026-06-25T12:23:05.694Z",
    "dateReserved": "2026-04-10T07:11:39.060Z",
    "dateUpdated": "2026-06-25T13:56:22.793Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-40209",
      "date": "2026-09-29",
      "epss": "0.007",
      "percentile": "0.51304"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "collectionURL": "https://repo.powerdns.com/",
                "defaultStatus": "unaffected",
                "modules": [
                  "DNS over TCP to the backend"
                ],
                "packageName": "dnsdist",
                "product": "DNSdist",
                "programFiles": [
                  "dnsdist-tcp-downstream.cc"
                ],
                "repo": "https://github.com/PowerDNS/pdns",
                "vendor": "PowerDNS",
                "versions": [
                  {
                    "lessThan": "1.9.15",
                    "status": "affected",
                    "version": "1.9.0",
                    "versionType": "semver"
                  },
                  {
                    "lessThan": "2.0.7",
                    "status": "affected",
                    "version": "2.0.0",
                    "versionType": "semver"
                  }
                ]
              }
            ],
            "source": "security@open-xchange.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors."
          }
        ],
        "id": "CVE-2026-40209",
        "lastModified": "2026-06-25T15:59:47.100",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "LOW",
                "baseScore": 5.3,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 1.4,
              "source": "security@open-xchange.com",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2026-40209",
                "options": [
                  {
                    "exploitation": "none"
                  },
                  {
                    "automatable": "yes"
                  },
                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-25T13:56:17.791790Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-06-25T13:16:39.527",
        "references": [
          {
            "source": "security@open-xchange.com",
            "url": "https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html"
          }
        ],
        "sourceIdentifier": "security@open-xchange.com",
        "vulnStatus": "Deferred",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-772"
              }
            ],
            "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "current_release_date": "2026-08-24T17:42:44+00:00",
      "cve": "CVE-2026-40209",
      "id": "CVE-2026-40209",
      "initial_release_date": "2026-06-25T12:23:05.694000+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "dnsdist: denial of service via IXFR queries",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40209.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-40209",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "yes"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-06-25T13:56:17.791790Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "problemTypes": [
              {
                "descriptions": [
                  {
                    "cweId": "CWE-772",
                    "description": "CWE-772 Missing Release of Resource after Effective Lifetime",
                    "lang": "en",
                    "type": "CWE"
                  }
                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-06-25T13:56:09.847Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "collectionURL": "https://repo.powerdns.com/",
              "defaultStatus": "unaffected",
              "modules": [
                "DNS over TCP to the backend"
              ],
              "packageName": "dnsdist",
              "product": "DNSdist",
              "programFiles": [
                "dnsdist-tcp-downstream.cc"
              ],
              "repo": "https://github.com/PowerDNS/pdns",
              "vendor": "PowerDNS",
              "versions": [
                {
                  "lessThan": "1.9.15",
                  "status": "affected",
                  "version": "1.9.0",
                  "versionType": "semver"
                },
                {
                  "lessThan": "2.0.7",
                  "status": "affected",
                  "version": "2.0.0",
                  "versionType": "semver"
                }
              ]
            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "finder",
              "value": "Qifan Zhang (Palo Alto Networks)"
            }
          ],
          "datePublic": "2026-06-24T22:00:00.000Z",
          "descriptions": [
            {
              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "\u003cp\u003eAn attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors.\u003c/p\u003e"
                }
              ],
              "value": "An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "LOW",
                "baseScore": 5.3,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
                "version": "3.1"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "description": "Missing Release of Resource after Effective Lifetime",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-06-25T12:23:05.694Z",
            "orgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981",
            "shortName": "OX"
          },
          "references": [
            {
              "url": "https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-09.html"
            }
          ],
          "source": {
            "discovery": "UNKNOWN"
          },
          "title": "Denial of service via IXFR queries",
          "x_generator": {
            "engine": "Vulnogram 1.0.2"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "8ce71d90-2354-404b-a86e-bec2cc4e6981",
        "assignerShortName": "OX",
        "cveId": "CVE-2026-40209",
        "datePublished": "2026-06-25T12:23:05.694Z",
        "dateReserved": "2026-04-10T07:11:39.060Z",
        "dateUpdated": "2026-06-25T13:56:22.793Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.