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CVE-2018-6557

Status: ModifiedHigh (7)—

The MOTD update script in the base-files package in Ubuntu 18.04 LTS before 10.1ubuntu2.2, and Ubuntu 18.10 before 10.1ubuntu6 incorrectly handled temporary files. A local attacker could use this issue to cause a denial of service, or possibly escalate privileges if kernel symlink restrictions were disabled.

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 (2)

Base-files Project — Base-filesCanonical — Ubuntu Linux

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2018-6557",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 4.4,
          "accessVector": "LOCAL",
          "vectorString": "AV:L/AC:M/Au:N/C:P/I:P/A:P",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 6.4,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 3.4,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1
      }
    ]
  },
  "affected": [
    {
      "source": "security@ubuntu.com",
      "affectedData": [
        {
          "vendor": "Ubuntu",
          "product": "base-files",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "10.1ubuntu2.2",
              "versionType": "custom"
            }
          ]
        }
      ]
    }
  ],
  "published": "2018-08-21T16:29:00.637",
  "references": [
    {
      "url": "http://www.securityfocus.com/bid/105148",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "security@ubuntu.com"
    },
    {
      "url": "http://www.securitytracker.com/id/1041530",
      "tags": [
        "Broken Link",
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "security@ubuntu.com"
    },
    {
      "url": "https://usn.ubuntu.com/3748-1/",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "security@ubuntu.com"
    },
    {
      "url": "http://www.securityfocus.com/bid/105148",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.securitytracker.com/id/1041530",
      "tags": [
        "Broken Link",
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://usn.ubuntu.com/3748-1/",
      "tags": [
        "Vendor 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": "The MOTD update script in the base-files package in Ubuntu 18.04 LTS before 10.1ubuntu2.2, and Ubuntu 18.10 before 10.1ubuntu6 incorrectly handled temporary files. A local attacker could use this issue to cause a denial of service, or possibly escalate privileges if kernel symlink restrictions were disabled."
    },
    {
      "lang": "es",
      "value": "El script de actualización de MOTD en el paquete de archivos base en Ubuntu 18.04 LTS en versiones anteriores a la 10.1ubuntu2.2 y Ubuntu 18.10 anteriores a la 10.1ubuntu6 manejaba incorrectamente los archivos temporales. Un atacante local podría usar este problema para provocar una denegación de servicio o posiblemente escalar privilegios si se desactivan las restricciones de enlaces simbólicos del kernel."
    }
  ],
  "lastModified": "2026-06-17T02:02:01.367",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:base-files_project:base-files:10.1ubuntu2.2:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "8A95C549-93EC-4A40-904F-7CFED2A94694"
            },
            {
              "criteria": "cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "23A7C53F-B80F-4E6A-AFA9-58EEA84BE11D"
            },
            {
              "criteria": "cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "07C312A0-CD2C-4B9C-B064-6409B25C278F"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security@ubuntu.com"
}