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CVE-2021-26720

Estado: ModificadaAlta (7.8)—

El archivo avahi-daemon-check-dns.sh en el paquete Debian avahi a versiones hasta 0.8-4, es ejecutado como root por medio de /etc/network/if-up.d/avahi-daemon, y permite a un atacante local causar una denegación de servicio o crear archivos vacíos arbitrarios por medio de un ataque de tipo symlink en archivos bajo /run/avahi-daemon. NOTA: esto solo afecta al empaquetado de Debian GNU/Linux (usado indirectamente por SUSE), no al producto de Avahi previo

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (2)

Avahi — AvahiDebian — Debian Linux

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-26720",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 4.6,
          "accessVector": "LOCAL",
          "vectorString": "AV:L/AC:L/Au:N/C:P/I:P/A:P",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 6.4,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 3.9,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-02-17T22:15:12.710",
  "references": [
    {
      "url": "https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824",
      "tags": [
        "Issue Tracking",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://bugzilla.suse.com/show_bug.cgi?id=1180827",
      "tags": [
        "Issue Tracking",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog",
      "tags": [
        "Broken Link",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://packages.debian.org/bullseye/avahi-daemon",
      "tags": [
        "Product",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://packages.debian.org/buster/avahi-daemon",
      "tags": [
        "Product",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://packages.debian.org/sid/avahi-daemon",
      "tags": [
        "Product",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://security-tracker.debian.org/tracker/CVE-2021-26720",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://www.openwall.com/lists/oss-security/2021/02/15/2",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824",
      "tags": [
        "Issue Tracking",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://bugzilla.suse.com/show_bug.cgi?id=1180827",
      "tags": [
        "Issue Tracking",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog",
      "tags": [
        "Broken Link",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://packages.debian.org/bullseye/avahi-daemon",
      "tags": [
        "Product",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://packages.debian.org/buster/avahi-daemon",
      "tags": [
        "Product",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://packages.debian.org/sid/avahi-daemon",
      "tags": [
        "Product",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://security-tracker.debian.org/tracker/CVE-2021-26720",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.openwall.com/lists/oss-security/2021/02/15/2",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-59"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon, and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE), not the upstream Avahi product."
    },
    {
      "lang": "es",
      "value": "El archivo avahi-daemon-check-dns.sh en el paquete Debian avahi a versiones hasta 0.8-4, es ejecutado como root por medio de /etc/network/if-up.d/avahi-daemon, y permite a un atacante local causar una denegación de servicio o crear archivos vacíos arbitrarios por medio de un ataque de tipo symlink en archivos bajo /run/avahi-daemon. NOTA: esto solo afecta al empaquetado de Debian GNU/Linux (usado indirectamente por SUSE), no al producto de Avahi previo"
    }
  ],
  "lastModified": "2026-06-17T03:43:43.297",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:avahi:avahi:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "7960274F-0D6F-4054-8236-145A6430B6CE",
              "versionEndIncluding": "0.8-4"
            }
          ],
          "operator": "OR"
        }
      ]
    },
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "DEECE5FC-CACF-4496-A3E7-164736409252"
            },
            {
              "criteria": "cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "07B237A9-69A3-4A9C-9DA0-4E06BD37AE73"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}