Eval Injection Vulnerability in NLTK Natural Language Toolkit
CVE-2025-71408

8.5HIGH

Key Information:

Vendor

Ntlk

Status
Ntlk
Vendor
CVE Published:
24 July 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2025-71408?

The Natural Language Toolkit (NLTK) version 3.9.3 and earlier are susceptible to an eval injection vulnerability within the nltk.collocations module. This security flaw arises when command-line arguments are directly passed to the eval() function in the main block of collocations.py, lacking proper validation or sanitization. An attacker controlling these arguments can execute arbitrary Python code, including operating system commands through the os module. This poses serious security risks, allowing unauthorized access and manipulation of the system. Users are urged to upgrade to the latest version to mitigate this vulnerability and protect their systems.

Affected Version(s)

ntlk 0

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2025-71408 - Proof of Concept

References

https://aydinnyunus.github.io/2026/06/07/command-injectio...
technical-descriptionexploit
https://github.com/nltk/nltk/releases/tag/3.9.3
release-notes
https://github.com/nltk/nltk/pull/3465
issue-tracking

CVSS V4

Score:
8.5
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Yunus AYDIN
.