ubuntu-cve-2020-25685
Vulnerability from osv_ubuntu
Published
2021-01-19 00:00
Modified
2026-05-26 19:47
Summary
Details

A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.

Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "dnsmasq",
            "binary_version": "2.68-1ubuntu0.2+esm6"
          },
          {
            "binary_name": "dnsmasq-base",
            "binary_version": "2.68-1ubuntu0.2+esm6"
          },
          {
            "binary_name": "dnsmasq-utils",
            "binary_version": "2.68-1ubuntu0.2+esm6"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:14.04:LTS",
        "name": "dnsmasq",
        "purl": "pkg:deb/ubuntu/dnsmasq@2.68-1ubuntu0.2+esm6?arch=source\u0026distro=esm-infra-legacy/trusty"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.66-4ubuntu1",
        "2.67-1",
        "2.68-1",
        "2.68-1ubuntu0.1",
        "2.68-1ubuntu0.2",
        "2.68-1ubuntu0.2+esm1",
        "2.68-1ubuntu0.2+esm2",
        "2.68-1ubuntu0.2+esm3",
        "2.68-1ubuntu0.2+esm5",
        "2.68-1ubuntu0.2+esm6"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "dnsmasq",
            "binary_version": "2.75-1ubuntu0.16.04.7"
          },
          {
            "binary_name": "dnsmasq-base",
            "binary_version": "2.75-1ubuntu0.16.04.7"
          },
          {
            "binary_name": "dnsmasq-utils",
            "binary_version": "2.75-1ubuntu0.16.04.7"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "dnsmasq",
        "purl": "pkg:deb/ubuntu/dnsmasq@2.75-1ubuntu0.16.04.7?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.75-1ubuntu0.16.04.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.75-1",
        "2.75-1ubuntu0.16.04.1",
        "2.75-1ubuntu0.16.04.2",
        "2.75-1ubuntu0.16.04.3",
        "2.75-1ubuntu0.16.04.4",
        "2.75-1ubuntu0.16.04.5"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "dnsmasq",
            "binary_version": "2.79-1ubuntu0.2"
          },
          {
            "binary_name": "dnsmasq-base",
            "binary_version": "2.79-1ubuntu0.2"
          },
          {
            "binary_name": "dnsmasq-base-lua",
            "binary_version": "2.79-1ubuntu0.2"
          },
          {
            "binary_name": "dnsmasq-utils",
            "binary_version": "2.79-1ubuntu0.2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "dnsmasq",
        "purl": "pkg:deb/ubuntu/dnsmasq@2.79-1ubuntu0.2?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.79-1ubuntu0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.78-1",
        "2.78-3",
        "2.79-1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "dnsmasq",
            "binary_version": "2.80-1.1ubuntu1.2"
          },
          {
            "binary_name": "dnsmasq-base",
            "binary_version": "2.80-1.1ubuntu1.2"
          },
          {
            "binary_name": "dnsmasq-base-lua",
            "binary_version": "2.80-1.1ubuntu1.2"
          },
          {
            "binary_name": "dnsmasq-utils",
            "binary_version": "2.80-1.1ubuntu1.2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "dnsmasq",
        "purl": "pkg:deb/ubuntu/dnsmasq@2.80-1.1ubuntu1.2?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.80-1.1ubuntu1.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.80-1ubuntu2",
        "2.80-1ubuntu4",
        "2.80-1.1ubuntu1"
      ]
    }
  ],
  "aliases": [],
  "details": "A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.",
  "id": "UBUNTU-CVE-2020-25685",
  "modified": "2026-05-26T19:47:00Z",
  "published": "2021-01-19T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2020-25685"
    },
    {
      "type": "REPORT",
      "url": "https://www.jsof-tech.com/disclosures/dnspooq/"
    },
    {
      "type": "REPORT",
      "url": "http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2021q1/014599.html"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-4698-1"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2020-25685"
    }
  ],
  "related": [
    "USN-4698-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2020-25685"
  ]
}



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