What is CVE-2026-79657?

CVE-2026-79657 is a critical-severity vulnerability in Nltk, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2026-08-25.

How severe is CVE-2026-79657?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Deserialization in Nltk

CVE-2026-79657

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.

Vulnerability class: Insecure Deserialization

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Nltk

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

References

disclosure@vulncheck.com (vendor-advisory)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-79657?: CVE-2026-79657 is a critical-severity vulnerability in Nltk, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2026-08-25.
How severe is CVE-2026-79657?: Critical severity. CVSS v3 base score is 9.8 out of 10.