Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-08-07T06:25:10 nltk: NLTK: Resource poisoning via improper package archive extraction 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N CWE-367

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.

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.

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, compromising data integrity in machine learning pipelines and affecting reproducibility-sensitive environments. Exploitation requires user interaction and has high attack complexity. Exploit Intelligence Out of support scope exploit-intelligence-tech-preview/vulnerability-analysis-rhel9 Lightspeed Core Fix deferred lightspeed-core/lightspeed-stack-rhel9 Lightspeed Core Fix deferred lightspeed-core/rag-tool-cpu-rhel9 Lightspeed Core Fix deferred lightspeed-core/rag-tool-cuda-12.9-rhel9 OpenShift Lightspeed Fix deferred openshift-lightspeed/lightspeed-ocp-rag-rhel9 OpenShift Lightspeed Fix deferred openshift-lightspeed/lightspeed-service-api-rhel9 OpenShift Lightspeed Fix deferred openshift-lightspeed-tech-preview/lightspeed-rag-tool-rhel9 Red Hat Ansible Automation Platform 2 Out of support scope ansible-automation-platform-25/lightspeed-chatbot-rhel8 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-llama-stack-core-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-pipeline-runtime-pytorch-llmcompressor-cuda-py312-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-ta-lmes-job-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-trustyai-garak-lls-provider-dsp-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-trustyai-nemo-guardrails-server-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-workbench-jupyter-pytorch-llmcompressor-cuda-py312-rhel9 https://www.cve.org/CVERecord?id=CVE-2026-12261 https://nvd.nist.gov/vuln/detail/CVE-2026-12261 https://huntr.com/bounties/8b8c381e-08a8-4e4f-bb46-a320c96a364f