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.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2025-71408US | — | — | ||
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 argu… | ||||
references
External citations — patches, advisories, analysis.
- https://aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/EVIDENCE
- https://github.com/advisories/GHSA-848c-c2cx-j7qxADVISORY
- https://github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0acFIX
- https://github.com/nltk/nltk/pull/3465FIX
- https://github.com/nltk/nltk/releases/tag/3.9.3ADVISORY
- https://www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-line-argumentsFIX
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