# CVE-2025-14009: nltk RCE — Fixed in 3.9.3 🐍 🐍 PyPI Not in CISA KEV HIGH severity # CVE-2025-14009 — nltk HIGH [Fix: nltk/nltk#3468](https://github.com/nltk/nltk/pull/3468) CVE-2025-14009 is a high-severity (CVSS 8.8) Code Injection vulnerability in nltk. A fix is available for nltk — see the affected versions and patch details below. Zip Slip Vulnerability in nltk/nltk Leading to Remote Code Execution Also known as[GHSA-7p94-766c-hgjp](/vulnerability/GHSA-7p94-766c-hgjp)PYSEC-2026-96 Published Feb 18, 2026 Updated Oct 28, 2026 Affected 1 pkg Patched 1 / 1 Exploits None indexed Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS) ## Exploitation Status ### Proof-of-concept exploit code exists - CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation. - CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks. - A successful exploit gives an attacker total control of the affected component, not partial access. Exploitation and automatability from CISA’s SSVC triage for CVE-2025-14009. ## EPSS Exploitation Probability [via FIRST.org ↗](https://www.first.org/epss/) 1.0%probability of exploitation in next 30 days Lower Risk0.00% Lower risk than most CVEs64th percentile — riskier than 64% of all scored CVEsHighest risk 0.29%0.71%1.12%1.54%0.9%1.0%May 26Sep 26Nov 26 Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/). ## How urgent is this, really ## Where this sits among everything scored ## Real-World Exposure 1 pkg affected 🐍`nltk` Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems. ## Description A critical vulnerability exists in the NLTK downloader component of nltk/nltk, affecting all versions. The \_unzip\_iter function in nltk/downloader.py uses zipfile.extractall() without performing path validation or security checks. This allows attackers to craft malicious zip packages that, when downloaded and extracted by NLTK, can execute arbitrary code. The vulnerability arises because NLTK assumes all downloaded packages are trusted and extracts them without validation. If a malicious package contains Python files, such as **init**.py, these files are executed automatically upon import, leading to remote code execution. This issue can result in full system compromise, including file system access, network access, and potential persistence mechanisms. ## Affected Packages 1 total 1 fixed Ecosystem Package Vulnerable range Fix 🐍PyPI `nltk` all versions 3.9.3`pip install --upgrade 'nltk==3.9.3'` ## Affected Products 1 product · 1 configurations Application `nltk`nltk < 3.9.3 range ## Detection & mitigation playbook Open-source dependency 1. ### Detect Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nltk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version. 2. ### Fix Update nltk to 3.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-14009 is resolved across your whole dependency graph. 3. ### Workarounds Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does. ## Fixing This On Your OS If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project. Red HatImportant The risk of this flaw to Red Hat products is mitigated by the default requirement that users authenticate before interacting with a system. This reduces the impact to Important. Red Hat products utilizing NLTK are only affected if they are configured to process untrustsed zip archives. Workaround published by Red Hat > Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Source: [Red Hat security advisory for CVE-2025-14009](https://access.redhat.com/security/cve/cve-2025-14009) (CC BY 4.0) Product Fixed in Advisory Red Hat OpenShift AI 2.25 `rhoai/odh-llama-stack-core-rhel9:1775144403` [RHSA-2026:10184](https://access.redhat.com/errata/RHSA-2026:10184) UbuntuCRITICAL [USN-8214-1Ubuntu](https://ubuntu.com/security/notices/USN-8214-1) ## Frequently Asked Questions A critical vulnerability exists in the NLTK downloader component of nltk/nltk, affecting all versions. The \_unzip\_iter function in nltk/downloader.py uses zipfile.extractall() without performing path validation or security checks. This allows attackers to craft malicious zip packages that, when downloaded and extracted by NLTK, can execute arbitrary code. The vulnerability arises because NLTK assumes all downloaded packages are trusted and extracts them without validation. If a malicious package contains Python files, such as \_\_init\_\_.py, these files are executed automatically upon import, lea O3 Security · Impact-Aware SCA ### Is CVE-2025-14009 in your dependencies? Find it across PyPI, including transitive dependencies. [Scan my dependencies](/book-demo) [How O3 SCA works](/impact-aware-sca)