nltk: NLTK: Arbitrary Code Execution via Eval Injection in Collocations Module (CVE-2025-71408)

Overview

A flaw was found in NLTK (Natural Language Toolkit). This eval injection vulnerability in the nltk.collocations module allows a local attacker to execute arbitrary Python code. By manipulating command-line arguments when collocations.py is invoked directly, an attacker can bypass validation and execute operating system commands. This can lead to significant impact on the system's confidentiality, integrity, and availability.

Vendor advisories

• Red Hat VEX · Important · affected: Exploit Intelligence, Red Hat Ansible Automation Platform 2, Red Hat OpenShift AI (RHOAI) · no fix planned: Exploit Intelligence, Red Hat Ansible Automation Platform 2, Red Hat OpenShift AI (RHOAI) · updated 2026-09-15 · vex

nltk: NLTK: Arbitrary Code Execution via Eval Injection in Collocations Module — rated Important by Red Hat. Released 2025-01-01, updated 2026-09-15.

Affected:

• Exploit Intelligence
• Red Hat Ansible Automation Platform 2
• Red Hat OpenShift AI (RHOAI)

No fix planned:

• Exploit Intelligence
• Red Hat Ansible Automation Platform 2
• Red Hat OpenShift AI (RHOAI)

Not affected:

• Lightspeed Core
• OpenShift Lightspeed
• Red Hat OpenShift AI (RHOAI)

Remediation

Will not fix

Workarounds / mitigations:

• To mitigate this vulnerability, avoid directly invoking the nltk.collocations module's internal script (collocations.py) with untrusted command-line arguments. In standard Red Hat deployments, NLTK is typically used as an imported library, which does not expose this vulnerability. If direct invocation is necessary, ensure that all command-line arguments are from trusted sources and are properly validated.

Package advisory (CVE-2025-71408)

Affected packages:

• nltk < 3.9.3

Patched in:

• nltk 3.9.3

Source: https://osv.dev/vulnerability/PYSEC-2026-3657