Is CVE-2026-79657 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-79657?

CVE-2026-79657 has a CVSS v3 severity of CRITICAL (9.8).

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CVE-2026-79657

Description

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.