RCE in Nltk
CVE-2025-71408
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.003 (17.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 17th percentile — 17.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
Weakness classification (CWE)
References
- aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/ (Exploit, technical-description, Third Party Advisory, exploit, Press/Media Coverage)
- github.com/nltk/nltk/releases/tag/3.9.3 (release-notes, Release Notes, patch)
- github.com/nltk/nltk/pull/3465 (issue-tracking, Patch, patch, Issue Tracking)
- github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0ac (Patch, patch)
- www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-li… (Patch, Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2025-71408?
- CVE-2025-71408 is a high-severity vulnerability in Nltk, classified under Eval Injection. CVSS score: 7.8/10. Published 2026-07-24.
- How severe is CVE-2025-71408?
- High severity. CVSS v3 base score is 7.8 out of 10.