NLTK: URL-Encoded Path Traversal in nltk.data.load() Allows Arbitrary Local File Read

{
  "id": "cf9e716306360efb62a9ffdb66796007a691da2b96279d2014f0d522c354bbf1",
  "url": "https://osv.dev/vulnerability/CVE-2026-54293",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "NLTK: URL-Encoded Path Traversal in nltk.data.load() Allows Arbitrary Local File Read",
    "summary": "NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. Prior to 3.10.0-rc1, nltk.data.load() in NLTK is vulnerable to path traversal via URL-encoded path separators and traversal segments when using the nltk: URL scheme. The unsafe-path regex check is performed before url2pathname() decodes the %xx sequences (a classic decode-after-check / TOCTOU-style flaw), allowing an attacker to bypass the protection documented in NLTK's SECURITY.md and read arbitrary files from the filesystem. While literal traversal strings such as ../../../etc/passwd are correctly blocked, encoded variants such as %2fetc%2fpasswd, %2e%2e%2f..., and ..%2f..%2f slip past the regex and are subsequently decoded into a real filesystem path. This vulnerability is fixed in 3.10.0-rc1.",
    "evidence": "osv:CVE-2026-54293",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-54293",
      "aliases": [
        "CVE-2026-54293",
        "GHSA-p4gq-832x-fm9v",
        "PYSEC-2026-2078"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/nltk/nltk",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "16a32d680d070254d5744e33fa83f9c0056d5a1f"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.10.0-rc1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "cpe": "cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.10.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.9.4",
            "3.9.3",
            "v3.9.2",
            "3.9.2",
            "3.9.1",
            "3.9",
            "3.8.2",
            "3.8.1",
            "3.8",
            "3.7",
            "3.6.7",
            "3.6.6",
            "3.6.5",
            "3.6.2",
            "3.6.1",
            "3.6",
            "3.5",
            "3.5b1",
            "3.4.4",
            "3.4.3",
            "3.4.1",
            "3.4",
            "3.3",
            "3.2.5",
            "3.2.4",
            "3.2.3",
            "3.2.2",
            "3.2.1",
            "3.2",
            "3.1",
            "3.0.5",
            "3.0.4",
            "3.0.3",
            "3.0.2",
            "3.0.0b1",
            "3.0a4",
            "2.0.1rc4",
            "2.0.1rc3",
            "2.0.1rc2",
            "2.0.1rc1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54293.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:32.346553178Z",
      "provider": "osv",
      "references": [
        "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-54293.json",
        "https://access.redhat.com/errata/RHSA-2026:42644",
        "https://access.redhat.com/errata/RHSA-2026:60520",
        "https://access.redhat.com/errata/RHSA-2026:65126",
        "https://access.redhat.com/security/cve/CVE-2026-54293",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54293.json",
        "https://github.com/nltk/nltk/security/advisories/GHSA-p4gq-832x-fm9v",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-54293",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2491486",
        "https://github.com/nltk/nltk/pull/3575"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-22"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54293.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-54293",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 499554,
  "published_at": "2026-06-22T17:25:05.611+00:00"
}