CVE-2026-12261
published 2026-08-07CVE-2026-12261: A vulnerability in `nltk.downloader` in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning. The downloader extracts package…
PriorityP433medium6.5CVSS 3.1
AVNACLPRNUIRSUCNIHAN
EPSS
0.21%
10.8th percentile
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.
Affected
17 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| ansible-automation-platform-25 | lightspeed-chatbot-rhel8 | — | — |
| exploit-intelligence-tech-preview | vulnerability-analysis-rhel9 | — | — |
| lightspeed-core | lightspeed-stack-rhel9 | — | — |
| lightspeed-core | rag-tool-cpu-rhel9 | — | — |
| lightspeed-core | rag-tool-cuda-12.9-rhel9 | — | — |
| nltk | nltk | <= 3.9.4 | — |
| nltk | nltk | >= 0 < 3.10.0 | 3.10.0 |
| nltk | nltk_nltk | unspecified – latest | — |
| openshift-lightspeed-tech-preview | lightspeed-rag-tool-rhel9 | — | — |
| openshift-lightspeed | lightspeed-ocp-rag-rhel9 | — | — |
| openshift-lightspeed | lightspeed-service-api-rhel9 | — | — |
| rhoai | odh-llama-stack-core-rhel9 | — | — |
| rhoai | odh-pipeline-runtime-pytorch-llmcompressor-cuda-py312-rhel9 | — | — |
| rhoai | odh-ta-lmes-job-rhel9 | — | — |
| rhoai | odh-trustyai-garak-lls-provider-dsp-rhel9 | — | — |
| rhoai | odh-trustyai-nemo-guardrails-server-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-pytorch-llmcompressor-cuda-py312-rhel9 | — | — |
CVSS provenance
nvdv3.16.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
nvdv3.05.3MEDIUMCVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
vendor_redhat5.3MEDIUM
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Red Hat
nltk: NLTK: Resource poisoning via improper package archive extraction
vendor_redhat·2026-08-07·CVSS 5.3
CVE-2026-12261 [MEDIUM] CWE-367 nltk: NLTK: Resource poisoning via improper package archive extraction
nltk: NLTK: Resource poisoning via improper package archive extraction
A flaw was found in the `nltk.downloader` component of NLTK. This vulnerability allows for cross-package resource and model poisoning. The downloader extracts package archives into shared namespaces and only validates package integrity after extraction. This design flaw enables one package to overwrite another package's trusted resources, leading to an integrity compromise that can affect machine learning pipelines and reproducibility-sensitive environments.
Statement: This Moderate impact vulnerability in NLTK's downloader component allows for cross-package resource poisoning. By extracting package archives into shared namespaces before integrity validation, an attacker could, indirectly, overwrite trusted resources,
VulDB
nltk up to 3.9.4 Downloader nltk.downloader code injection (Nessus ID 333363)
vuldb·2026-08-08·CVSS 5.3
CVE-2026-12261 [MEDIUM] nltk up to 3.9.4 Downloader nltk.downloader code injection (Nessus ID 333363)
A vulnerability labeled as critical has been found in nltk up to 3.9.4. The affected element is the function nltk.downloader of the component Downloader. Such manipulation leads to code injection.
This vulnerability is uniquely identified as CVE-2026-12261. The attack can be launched remotely. No exploit exists.
GHSA
NLTK downloader allows cross-package resource and model poisoning
ghsa·2026-08-07
CVE-2026-12261 [MEDIUM] CWE-284 NLTK downloader allows cross-package resource and model poisoning
NLTK downloader allows cross-package resource and model poisoning
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.
GHSA
A vulnerability in `nltk.downloader` in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning.
ghsa_unreviewed·2026-08-07
CVE-2026-12261 [MEDIUM] CWE-284 A vulnerability in `nltk.downloader` in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning.
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.
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-12261 python-nltk: NLTK: Resource poisoning via improper package archive extraction [epel-all]
bugzilla·2026-08-07·CVSS 5.3
CVE-2026-12261 [MEDIUM] CVE-2026-12261 python-nltk: NLTK: Resource poisoning via improper package archive extraction [epel-all]
CVE-2026-12261 python-nltk: NLTK: Resource poisoning via improper package archive extraction [epel-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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 cha
Bugzilla
CVE-2026-12261 nltk: NLTK: Resource poisoning via improper package archive extraction
bugzilla·2026-08-07·CVSS 5.3
CVE-2026-12261 [MEDIUM] CVE-2026-12261 nltk: NLTK: Resource poisoning via improper package archive extraction
CVE-2026-12261 nltk: NLTK: Resource poisoning via improper package archive extraction
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.
Bugzilla
CVE-2026-12261 python-nltk: NLTK: Resource poisoning via improper package archive extraction [fedora-all]
bugzilla·2026-08-07·CVSS 5.3
CVE-2026-12261 [MEDIUM] CVE-2026-12261 python-nltk: NLTK: Resource poisoning via improper package archive extraction [fedora-all]
CVE-2026-12261 python-nltk: NLTK: Resource poisoning via improper package archive extraction [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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 c
2026-08-07
Published