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.
Fix
Patch, vendor advisory and mitigation references on NVD 2
- https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw Exploit, Vendor Advisory
- https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw Exploit, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 9.3 · nltkNVD modified 2026-10-08 16:17
Affected (CPE criteria) 1
cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*
References 3
- https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw Exploit, Vendor Advisory
- https://www.vulncheck.com/advisories/nltk-before-3.10.3-remote-code-execution-via-unsafe-pickle-deserialization Third Party Advisory
- https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfw Exploit, Vendor Advisory