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CVE-2026-81725

Estado: AnalizadaMedia (6.3)—

NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.

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)

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  "id": "CVE-2026-81725",
  "cveTags": [],
  "metrics": {
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          "id": "CVE-2026-81725",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
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          "version": "2.0.3",
          "timestamp": "2026-08-27T18:24:00.717908Z"
        }
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    "cvssMetricV31": [
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        "cvssData": {
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          "version": "3.1",
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          "baseSeverity": "LOW",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "LOW",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 2.2
      }
    ],
    "cvssMetricV40": [
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        "type": "Secondary",
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        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
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          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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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          "vulnIntegrityImpact": "NONE",
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          "modifiedAttackRequirements": "NOT_DEFINED",
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          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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  "affected": [
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      "affectedData": [
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          "versions": [
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  "published": "2026-08-27T17:21:03.247",
  "references": [
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      "url": "https://github.com/nltk/nltk/security/advisories/GHSA-8mpw-7fpc-4gqj",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "source": "disclosure@vulncheck.com"
    },
    {
      "url": "https://www.vulncheck.com/advisories/nltk-before-3.10.3-regular-expression-denial-of-service-via-pl196xcorpusreader",
      "tags": [
        "Third Party Advisory"
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  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "description": [
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          "value": "CWE-400"
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    {
      "lang": "en",
      "value": "NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth."
    }
  ],
  "lastModified": "2026-09-01T20:06:33.420",
  "configurations": [
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}