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PYSEC-2026-3735

Quick fix

PYSEC-2026-3735 — nltk: upgrade to the fixed version with the command below.

pip install --upgrade 'nltk>=3.10.3'

Details

NLTK 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. Attackers can craft malicious pickle payloads invoking dangerous in-namespace functions like ReppTokenizer._execute and numpy.f2py.crackfortran.myeval through pickle REDUCE to execute arbitrary commands during model or tokenizer artifact loading.

Are you affected?

Enter the version of the package you're using.

Affected packages

PyPI/nltk

Introduced in: 0Fixed in: 3.10.3

Fixpip install --upgrade 'nltk>=3.10.3'

References

https://www.vulncheck.com/advisories/nltk-before-3.10.3-remote-code-execution-via-unsafe-pickle-deserialization[ADVISORY]
https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw[EVIDENCE]