GHSA-ffj6-66c4-86gw

Suggest an improvement
Source
https://github.com/advisories/GHSA-ffj6-66c4-86gw
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-ffj6-66c4-86gw/GHSA-ffj6-66c4-86gw.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-ffj6-66c4-86gw
Aliases
Downstream
Published
2026-08-07T09:31:52Z
Modified
2026-10-02T23:40:50Z
Severity
  • 5.3 (Medium) CVSS_V3 - CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N CVSS Calculator
Summary
NLTK downloader allows cross-package resource and model poisoning
Details

A vulnerability in nltk.downloader in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning. The downloader extracts package archives into shared namespaces such as corpora/ and taggers/ instead of package-isolated roots, and validates package integrity only after the archive has been written and extracted. This design flaw enables one package to overwrite another package's trusted resources within the same namespace, making the changes immediately active through ordinary NLTK APIs. This issue persists across fresh interpreter restarts and can affect downstream workflows, including machine learning pipelines and reproducibility-sensitive environments.

Database specific 
{
    "cwe_ids":  [
        "CWE-284"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-10-02T23:09:22Z",
    "nvd_published_at":  "2026-08-07T07:16:26Z",
    "severity":  "MODERATE"
}
References

Affected packages

PyPI / nltk

Package

Name
nltk
View open source insights on deps.dev
Purl
pkg:pypi/nltk

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
3.10.0

Affected versions

2.*
2.0.1rc2-git
2.0b4
2.0b5
2.0b6
2.0b7
2.0b8
2.0b9
2.0.1rc1
2.0.1rc3
2.0.1rc4
2.0.1
2.0.2
2.0.3
2.0.4
2.0.5
0.*
0.8
0.9
0.9.3
0.9.4
0.9.5
0.9.6
0.9.7
0.9.8
0.9.9
3.*
3.0.0b1
3.0.0b2
3.0.0
3.0.1
3.0.2
3.0.3
3.0.4
3.0.5
3.1
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.3
3.4
3.4.1
3.4.2
3.4.3
3.4.4
3.4.5
3.5b1
3.5
3.6
3.6.1
3.6.2
3.6.3
3.6.4
3.6.5
3.6.6
3.6.7
3.7
3.8
3.8.1
3.9b1
3.9
3.9.1
3.9.2
3.9.3
3.9.4

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-ffj6-66c4-86gw/GHSA-ffj6-66c4-86gw.json"