ubuntu-cve-2025-5994
Vulnerability from osv_ubuntu
Published
2025-07-17 00:00
Modified
2026-06-02 19:38
Summary
Details

A multi-vendor cache poisoning vulnerability named 'Rebirthday Attack' has been discovered in caching resolvers that support EDNS Client Subnet (ECS). Unbound is also vulnerable when compiled with ECS support, i.e., '--enable-subnet', AND configured to send ECS information along with queries to upstream name servers, i.e., at least one of the 'send-client-subnet', 'client-subnet-zone' or 'client-subnet-always-forward' options is used. Resolvers supporting ECS need to segregate outgoing queries to accommodate for different outgoing ECS information. This re-opens up resolvers to a birthday paradox attack (Rebirthday Attack) that tries to match the DNS transaction ID in order to cache non-ECS poisonous replies.

Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/R:U/V:C
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libunbound2",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
          },
          {
            "binary_name": "python-unbound",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.4.22-1ubuntu4.14.04.3+esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:14.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.4.22-1ubuntu4.14.04.3+esm3?arch=source\u0026distro=esm-infra-legacy/trusty"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.4.20-1",
        "1.4.21-1",
        "1.4.21-1ubuntu1",
        "1.4.21-1ubuntu2",
        "1.4.22-1ubuntu1",
        "1.4.22-1ubuntu2",
        "1.4.22-1ubuntu3",
        "1.4.22-1ubuntu4",
        "1.4.22-1ubuntu4.14.04.1",
        "1.4.22-1ubuntu4.14.04.2",
        "1.4.22-1ubuntu4.14.04.3",
        "1.4.22-1ubuntu4.14.04.3+esm1",
        "1.4.22-1ubuntu4.14.04.3+esm2",
        "1.4.22-1ubuntu4.14.04.3+esm3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libunbound2",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
          },
          {
            "binary_name": "python-unbound",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.5.8-1ubuntu1.1+esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.5.8-1ubuntu1.1+esm3?arch=source\u0026distro=esm-infra-legacy/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.4.22-1ubuntu6",
        "1.5.7-1ubuntu1",
        "1.5.7-1ubuntu2",
        "1.5.8-1ubuntu1",
        "1.5.8-1ubuntu1.1",
        "1.5.8-1ubuntu1.1+esm1",
        "1.5.8-1ubuntu1.1+esm2",
        "1.5.8-1ubuntu1.1+esm3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libunbound2",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
          },
          {
            "binary_name": "python-unbound",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.6.7-1ubuntu2.6+esm4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.6.7-1ubuntu2.6+esm4?arch=source\u0026distro=esm-infra/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.5-1",
        "1.6.7-1",
        "1.6.7-1build1",
        "1.6.7-1ubuntu1",
        "1.6.7-1ubuntu2",
        "1.6.7-1ubuntu2.1",
        "1.6.7-1ubuntu2.2",
        "1.6.7-1ubuntu2.3",
        "1.6.7-1ubuntu2.4",
        "1.6.7-1ubuntu2.5",
        "1.6.7-1ubuntu2.6",
        "1.6.7-1ubuntu2.6+esm2",
        "1.6.7-1ubuntu2.6+esm3",
        "1.6.7-1ubuntu2.6+esm4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libunbound8",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          },
          {
            "binary_name": "python-unbound",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.9.4-2ubuntu1.11+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.9.4-2ubuntu1.11+esm1?arch=source\u0026distro=esm-infra/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.9.0-2ubuntu1",
        "1.9.0-2ubuntu2",
        "1.9.4-2",
        "1.9.4-2ubuntu1",
        "1.9.4-2ubuntu1.1",
        "1.9.4-2ubuntu1.2",
        "1.9.4-2ubuntu1.3",
        "1.9.4-2ubuntu1.4",
        "1.9.4-2ubuntu1.5",
        "1.9.4-2ubuntu1.6",
        "1.9.4-2ubuntu1.8",
        "1.9.4-2ubuntu1.9",
        "1.9.4-2ubuntu1.11",
        "1.9.4-2ubuntu1.11+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libunbound8",
            "binary_version": "1.13.1-1ubuntu5.11"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.13.1-1ubuntu5.11"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.13.1-1ubuntu5.11"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.13.1-1ubuntu5.11"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.13.1-1ubuntu5.11"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.13.1-1ubuntu5.11?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.13.1-1ubuntu5.11"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.13.1-1ubuntu1",
        "1.13.1-1ubuntu3",
        "1.13.1-1ubuntu5",
        "1.13.1-1ubuntu5.1",
        "1.13.1-1ubuntu5.2",
        "1.13.1-1ubuntu5.3",
        "1.13.1-1ubuntu5.4",
        "1.13.1-1ubuntu5.5",
        "1.13.1-1ubuntu5.7",
        "1.13.1-1ubuntu5.8",
        "1.13.1-1ubuntu5.10"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libunbound8",
            "binary_version": "1.19.2-1ubuntu3.5"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.19.2-1ubuntu3.5"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.19.2-1ubuntu3.5"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.19.2-1ubuntu3.5"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.19.2-1ubuntu3.5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.19.2-1ubuntu3.5?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.19.2-1ubuntu3.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.17.1-2",
        "1.18.0-2ubuntu1",
        "1.18.0-2ubuntu2",
        "1.19.1-1ubuntu1",
        "1.19.2-1ubuntu1",
        "1.19.2-1ubuntu3",
        "1.19.2-1ubuntu3.1",
        "1.19.2-1ubuntu3.2",
        "1.19.2-1ubuntu3.3",
        "1.19.2-1ubuntu3.4"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libunbound8",
            "binary_version": "1.22.0-2ubuntu1"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.22.0-2ubuntu1"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.22.0-2ubuntu1"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.22.0-2ubuntu1"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.22.0-2ubuntu1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.22.0-2ubuntu1?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.22.0-2ubuntu1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.22.0-1ubuntu1"
      ]
    }
  ],
  "aliases": [],
  "details": "A multi-vendor cache poisoning vulnerability named \u0027Rebirthday Attack\u0027 has been discovered in caching resolvers that support EDNS Client Subnet (ECS). Unbound is also vulnerable when compiled with ECS support, i.e., \u0027--enable-subnet\u0027, AND configured to send ECS information along with queries to upstream name servers, i.e., at least one of the \u0027send-client-subnet\u0027, \u0027client-subnet-zone\u0027 or \u0027client-subnet-always-forward\u0027 options is used. Resolvers supporting ECS need to segregate outgoing queries to accommodate for different outgoing ECS information. This re-opens up resolvers to a birthday paradox attack (Rebirthday Attack) that tries to match the DNS transaction ID in order to cache non-ECS poisonous replies.",
  "id": "UBUNTU-CVE-2025-5994",
  "modified": "2026-06-02T19:38:44Z",
  "published": "2025-07-17T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2025-5994"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-5994"
    },
    {
      "type": "REPORT",
      "url": "https://nlnetlabs.nl/downloads/unbound/CVE-2025-5994.txt"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-7666-1"
    }
  ],
  "related": [
    "USN-7666-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/R:U/V:C",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2025-5994"
  ]
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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