CVE-2026-12261

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Source
https://cve.org/CVERecord?id=CVE-2026-12261
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-12261.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-12261
Aliases
Downstream
Published
2026-08-07T06:25:10Z
Modified
2026-09-10T13:11:08Z
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
Improper Access Control in nltk/nltk
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 
{
    "cna_assigner": "@huntr_ai",
    "cwe_ids": [
        "CWE-284"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/12xxx/CVE-2026-12261.json"
}
References

Affected packages

Git / github.com/nltk/nltk

Affected ranges

Type
GIT
Repo
https://github.com/nltk/nltk
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Last Affected
ad9c96ba00a16923ffe917eacf63f1707bfa2d08
Database specific
Show details 
{
    "cpe": "cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*",
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "last_affected": "3.9.4"
        }
    ],
    "source": "CPE_RANGE"
}

Affected versions

2.*
2.0.1rc1
2.0.1rc2
2.0.1rc3
2.0.1rc4
3.*
3.0.0b1
3.0.2
3.0.3
3.0.4
3.0.5
3.0a4
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
3.4.3
3.4.4
3.5
3.5b1
3.6
3.6.1
3.6.2
3.6.5
3.6.6
3.6.7
3.7
3.8
3.8.1
3.8.2
3.9
3.9.1
3.9.2
3.9.3
3.9.4
v3.*
v3.9.2

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-12261.json"