Bug 2506944 (CVE-2025-71408)

Summary: CVE-2025-71408 nltk: NLTK: Arbitrary Code Execution via Eval Injection in Collocations Module
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: anpicker, bparees, dschmidt, ebourniv, hasun, jfula, jlanda, jowilson, kshier, nyancey, ometelka, ptisnovs, sbunciak, simaishi, stcannon, syedriko, teagle, xdharmai, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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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.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2528394, 2528395    
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Description OSIDB Bzimport 2026-07-24 22:01:29 UTC 
NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the __main__ block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.