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CVE-2026-81727

Estado: AnalizadaMedia (6.9)—

NLTK versions before 3.10.3 contain a filesystem containment bypass vulnerability in the Downloader.download and Downloader.incr_download methods that allows attackers to overwrite files outside the install root through pre-existing hardlinks. Attackers with write access to a shared downloader directory can create hardlinks pointing to outside-root files that are then overwritten during normal package extraction, mutating files outside the intended install tree.

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 (1)

Nltk — Nltk

CWE

Referencias

JSON original (NVD)

Mostrar
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  "id": "CVE-2026-81727",
  "cveTags": [],
  "metrics": {
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          "id": "CVE-2026-81727",
          "role": "CISA Coordinator",
          "options": [
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              "automatable": "no"
            },
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              "technicalImpact": "partial"
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          ],
          "version": "2.0.3",
          "timestamp": "2026-08-27T17:43:29.016552Z"
        }
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    "cvssMetricV31": [
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          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
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          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 5.2,
        "exploitabilityScore": 1.8
      }
    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
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        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
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          "Automatable": "NOT_DEFINED",
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
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          "modifiedAttackRequirements": "NOT_DEFINED",
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          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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          "product": "nltk",
          "versions": [
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              "version": "0",
              "lessThan": "3.10.3",
              "versionType": "semver"
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              "version": "3.10.3",
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  "published": "2026-08-27T17:21:03.533",
  "references": [
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      "url": "https://github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672",
      "tags": [
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        "Vendor Advisory"
      ],
      "source": "disclosure@vulncheck.com"
    },
    {
      "url": "https://www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downloader",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "disclosure@vulncheck.com"
    },
    {
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      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
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  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "description": [
        {
          "lang": "en",
          "value": "CWE-59"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "NLTK versions before 3.10.3 contain a filesystem containment bypass vulnerability in the Downloader.download and Downloader.incr_download methods that allows attackers to overwrite files outside the install root through pre-existing hardlinks. Attackers with write access to a shared downloader directory can create hardlinks pointing to outside-root files that are then overwritten during normal package extraction, mutating files outside the intended install tree."
    }
  ],
  "lastModified": "2026-08-31T19:08:45.560",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "versionEndExcluding": "3.10.3"
            }
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          "operator": "OR"
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      ]
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  ],
  "sourceIdentifier": "disclosure@vulncheck.com"
}