[GHSA-pv39-qrfq-g8gc] In nltk version 3.9.4, the `nltk.downloader.Downloader...

advisories/unreviewed/2026/08/GHSA-pv39-qrfq-g8gc/GHSA-pv39-qrfq-g8gc.json

@@ -1,24 +1,46 @@
 {
   "schema_version": "1.4.0",
   "id": "GHSA-pv39-qrfq-g8gc",
-  "modified": "2026-08-03T09:32:37Z",
+  "modified": "2026-08-03T09:32:38Z",
   "published": "2026-08-03T09:32:37Z",
   "aliases": [
     "CVE-2026-12259"
   ],
+  "summary": "NLTK Checksum Validation Bypass in Package Downloads",
   "details": "In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package bytes to disk and may extract them before enforcing SHA-256 or MD5 checksum validation. This allows an attacker to tamper with the package response body for `info.url` through a compromised mirror, malicious proxy, or other source-substitution condition, leading to the installation of attacker-controlled package bytes. The vulnerability can result in malicious corpus or model content being trusted by downstream users or applications.",
   "severity": [
     {
       "type": "CVSS_V3",
       "score": "CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N"
     }
   ],
-  "affected": [],
+  "affected": [
+    {
+      "package": {
+        "ecosystem": "PyPI",
+        "name": "nltk"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "0"
+            }
+          ]
+        }
+      ]
+    }
+  ],
   "references": [
     {
       "type": "ADVISORY",
       "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-12259"
     },
+    {
+      "type": "PACKAGE",
+      "url": "https://github.com/nltk/nltk"
+    },
     {
       "type": "WEB",
       "url": "https://huntr.com/bounties/659ccf6d-12d4-4d4a-84c0-078633c35a5d"