CVE-2025-71408NLTK < 3.9.3 Eval Injection via collocations.py Command-Line Arguments
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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.
- CVSS
- 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-95
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- VulnCheck
- NVD analysis
- Analyzed
- Record last updated
- Oct 8, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
References
- https://aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/technical-description, exploit
- https://github.com/nltk/nltk/releases/tag/3.9.3release-notes, patch
- https://github.com/nltk/nltk/pull/3465issue-tracking, patch
- https://github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0acpatch
- https://www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-line-argumentsthird-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.