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CVE-2018-20835

Status: ModifiedHigh (7.5)—

A vulnerability was found in tar-fs before 1.16.2. An Arbitrary File Overwrite issue exists when extracting a tarball containing a hardlink to a file that already exists on the system, in conjunction with a later plain file with the same name as the hardlink. This plain file content replaces the existing file content.

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)

Tar-fs Project — Tar-fs

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2018-20835",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 6.4,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:N/I:P/A:P",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 4.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV30": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.0",
          "baseScore": 7.5,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2019-04-30T19:29:03.437",
  "references": [
    {
      "url": "https://github.com/mafintosh/tar-fs/commit/06672828e6fa29ac8551b1b6f36c852a9a3c58a2",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://github.com/mafintosh/tar-fs/compare/d590fc7...a35ce2f",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://hackerone.com/reports/344595",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://github.com/mafintosh/tar-fs/commit/06672828e6fa29ac8551b1b6f36c852a9a3c58a2",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://github.com/mafintosh/tar-fs/compare/d590fc7...a35ce2f",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://hackerone.com/reports/344595",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A vulnerability was found in tar-fs before 1.16.2. An Arbitrary File Overwrite issue exists when extracting a tarball containing a hardlink to a file that already exists on the system, in conjunction with a later plain file with the same name as the hardlink. This plain file content replaces the existing file content."
    },
    {
      "lang": "es",
      "value": "Fue encontrada una vulnerabilidad en tar-FS anterior a la versión 1.16.2. Existe un problema de sobrescritura de archivo arbitrario cuando se extrae un tarball que contiene un hardlink en un archivo que ya existe en el sistema, junto con un archivo sin formato con el mismo nombre que el hardlink. Este contenido de archivo sin formato reemplaza el contenido del archivo existente."
    }
  ],
  "lastModified": "2026-06-17T01:53:33.670",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:tar-fs_project:tar-fs:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "7E1491BB-6958-42D5-A79C-37BD0095BC77",
              "versionEndExcluding": "1.16.2"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}