Vulnerabilities in pkg:pypi/nltk

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2jhm-w3mp-jcwr",
  "modified" : "2026-10-02T23:11:23Z",
  "published" : "2026-08-10T00:31:42Z",
  "aliases" : [ "CVE-2026-12372" ],
  "summary" : "NLTK network URL validation permits SSRF to RFC 6598 shared-address-space hosts",
  "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "nltk"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.10.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-12372"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nltk/nltk/commit/4a820afa58810cd05049b6c6eae306694d6cfe65"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nltk/nltk"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nltk/nltk/releases/tag/v3.10.0"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3955.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://huntr.com/bounties/2911b643-571c-42e4-b0c2-9a1fa6f491db"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-02T23:11:23Z",
    "nvd_published_at" : "2026-08-09T23:16:35Z"
  }
}