CVE-2025-14009High· 8.8▾ TwilightA 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 a…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 48.4 · likelihood 0.2 · exploitation 0
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Exploit-prediction probability, daily snapshots since Aug 2.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.8%
0.8% → 1.0%
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.
nltk < 3.9.3Upgrade past the affected range:
nltk 3.9.3Affected packages:
nltk < 3.9.3Patched in:
nltk 3.9.3Source: https://osv.dev/vulnerability/GHSA-7p94-766c-hgjp
Connected by shared product, vendor, weakness, or advisory.
CVE-2026-33236High· 8.1NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing
CVE-2026-12252High· 7.8In nltk/nltk versions 3.9.3 and earlier, five Stanford interface classes (StanfordPOSTagger, StanfordNERTagger, StanfordParser, StanfordDependencyParser, and StanfordNeuralDependencyParser) are vulnerable to untrusted JAR code execution.…
CVE-2026-12261Medium· 6.5A vulnerability in `nltk.downloader` in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning
CVE-2026-12259Medium· 6.5In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package bytes to disk and may extract them before enforcing SHA-256 or MD5 checksum validation
CVE-2026-79657Critical· 9.8NLTK versions before 3.10.3 contain a remote code execution vulnerability in allowlisted pickle loaders that trust entire module namespaces instead of specific safe callables
CVE-2026-78683Critical· 9.6NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py)