Improper Input Validation in nltk/nltk (nltk nltk/nltk)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.10 % · percentile 1 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- @huntr_ai
- NVD status
- Analyzed
Description
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.
Weaknesses (CWE)
- CWE-494 — Download of Code Without Integrity Check
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.0 | MEDIUM 5.3 | CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N | @huntr_ai |
| CVSS 3.1 | MEDIUM 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N | NVD · nvd@nist.gov (Primary) |
| CVSS 3.0 | MEDIUM 5.3 | CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N | NVD · security@huntr.dev (Secondary) |
Advisories
- GHSA-5wp5-5229-5g6q — NLTK: Missing Post-Download Integrity Verification Allows Malicious Package Injection
- GHSA-gf32-cmjh-8m9v — Duplicate Advisory: NLTK: Missing Post-Download Integrity Verification Allows Malicious Package Injection
- PYSEC-2026-3729 — NLTK before 3.9.3 fails to verify file integrity after downloading packages and before extraction in the downloader module. Attackers can perform man-in-the-mid
- PYSEC-2026-4318 — In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package bytes to disk and may extract them before enforci
European references
- ENISA EUVD · EUVD-2026-52226
- GCVE · GCVE-0-2026-12259
Affected configurations (NVD CPE)
cpe:2.3:a:nltk:nltk:3.9.4:*:*:*:*:*:*:*
Affected products
| Product | Versions |
|---|---|
| nltk · nltk/nltk | affected unspecified ≤ latest |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |