CVE-2026-79657
Received Received - Intake

NLTK Remote Code Execution via Unsafe Pickle Loading

Publication date: 2026-08-25

Last updated on: 2026-08-25

Assigner: VulnCheck

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.

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Meta Information

Published
2026-08-25
Last Modified
2026-08-25
Generated
2026-08-25
AI Q&A
2026-08-25
EPSS Evaluated
N/A
NVD
CVE-2026-79657
EUVD
EUVD-2026-65440

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
nltk nltk to 3.10.3 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-502 The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

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Executive Summary

This vulnerability in NLTK versions before 3.10.3 allows remote code execution due to unsafe pickle deserialization. The library trusts entire module namespaces instead of specific safe functions during unpickling. Attackers can craft malicious pickle payloads to invoke dangerous functions like ReppTokenizer._execute or numpy.f2py.crackfortran.myeval, executing arbitrary commands when loading models or tokenizers.

Detection Guidance

Check NLTK version with pip show nltk. If version is below 3.10.3, the system is vulnerable. Inspect logs for unusual pickle loading activity or command execution during model/tokenizer loading.

Impact Analysis

If you use NLTK versions before 3.10.3, an attacker could exploit this to run arbitrary code on your system. This could lead to data theft, system compromise, or further network infiltration. The attack requires no privileges or user interaction and can be triggered remotely.

Compliance Impact

This vulnerability could lead to unauthorized data access or exfiltration, violating GDPR's data protection requirements and HIPAA's safeguards for protected health information. Organizations may face compliance penalties if exploited due to inadequate security controls.

Mitigation Strategies

Upgrade NLTK to version 3.10.3 or later immediately. Review and restrict pickle deserialization in applications using NLTK. Monitor for suspicious activity related to model or tokenizer loading.

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