{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:nltk:nltk:3.9.4:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "3.9.4"
              },
              {
                "last_affected": "3.9.4"
              }
            ],
            "source": "CPE_STRING"
          },
          "events": [
            {
              "introduced": "ad9c96ba00a16923ffe917eacf63f1707bfa2d08"
            },
            {
              "last_affected": "ad9c96ba00a16923ffe917eacf63f1707bfa2d08"
            }
          ],
          "repo": "https://github.com/nltk/nltk",
          "type": "GIT"
        }
      ],
      "versions": [
        "3.9.4"
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "@huntr_ai",
    "cwe_ids": [
      "CWE-918"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12372.json"
  },
  "details": "A Server-Side Request Forgery (SSRF) vulnerability exists in nltk/nltk versions 3.9.4 and the current develop branch. The `nltk.pathsec.validate_network_url()` function, intended to prevent SSRF by rejecting internal network addresses, fails to reject IPs in the RFC 6598 shared address space (`100.64.0.0/10`). This occurs because Python's `ipaddress` module does not classify such addresses as `is_private` or `is_global`, and the current guard only checks `is_private` and a few explicit categories. An attacker who can influence a URL passed to NLTK's network-loading helpers can exploit this vulnerability to make a strict-mode application send requests to shared-address-space hosts, potentially exposing non-public infrastructure reachable from the application host. The impact is limited to SSRF-style confidentiality exposure, with no code execution claimed.",
  "id": "CVE-2026-12372",
  "modified": "2026-09-06T03:30:42.764292554Z",
  "published": "2026-08-09T22:45:52.799Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://huntr.com/bounties/2911b643-571c-42e4-b0c2-9a1fa6f491db"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12372.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-12372"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Server-Side Request Forgery (SSRF) in nltk/nltk"
}