{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "3.6"
                  },
                  {
                    "fixed": "3.10.4"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              },
              {
                "range": [
                  {
                    "introduced": "3.6"
                  },
                  {
                    "fixed": "3.10.4"
                  }
                ],
                "source": "DESCRIPTION"
              }
            ]
          },
          "events": [
            {
              "introduced": "24d6e0d4123a5cfea3ede7dbdfe77fe0ec54b83c"
            },
            {
              "fixed": "5c41fc04a45e95577a83f3914acda211a994be00"
            }
          ],
          "repo": "https://github.com/nltk/nltk",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-gpwc-27cw-rh9r"
  ],
  "database_specific": {
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
      "CWE-407"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/126xxx/CVE-2026-126301.json"
  },
  "details": "NLTK from 3.6 before 3.10.4 contains an algorithmic complexity vulnerability in LegalitySyllableTokenizer.tokenize that allows remote attackers to exhaust CPU by supplying long all-vowel tokens. Attackers can submit a token such as a long run of vowels, causing the unguarded onset reversal loop to perform quadratic work and deny service to syllabification components.",
  "id": "CVE-2026-126301",
  "modified": "2026-11-15T02:30:31.685250034Z",
  "published": "2026-11-13T09:36:25.223Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/126xxx/CVE-2026-126301.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/nltk/nltk/security/advisories/GHSA-gpwc-27cw-rh9r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-126301"
    },
    {
      "type": "ADVISORY",
      "url": "https://www.vulncheck.com/advisories/nltk-from-3.6-before-3.10.4-quadratic-cpu-exhaustion-via-legalitysyllabletokenizer-tokenize"
    }
  ],
  "schema_version": "1.9.2",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "NLTK from 3.6 before 3.10.4 Quadratic CPU Exhaustion via LegalitySyllableTokenizer.tokenize"
}