CVE-2025-71408

high

Description

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.

References

https://www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-line-arguments

https://aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/

https://github.com/nltk/nltk/releases/tag/3.9.3

https://github.com/nltk/nltk/pull/3465

https://github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0ac

Details

Source: Mitre, NVD

Published: 2026-07-24

Updated: 2026-08-10

Risk Information

CVSS v2

Base Score: 6.8

Vector: CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C

Severity: Medium

CVSS v3

Base Score: 7.8

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Severity: High

CVSS v4

Base Score: 8.5

Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Severity: High

EPSS

EPSS: 0.00158