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.
- CVSS 4.0
- 8.5
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 - CVSS 3.1
- 7.8
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS
- 0.3% chance of exploitation in the next 30 days; higher than 18% of CVEs (scores of 2026-10-25)
- CWE
- CWE-95
- Published
- Modified
- Record from
- the NVD, synced
Affected
- nltk:nltk
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-848c-c2cx-j7qx | PyPI | nltk | <3.9.3 | 3.9.3 |
| PYSEC-2026-3657 | PyPI | nltk | <3.9.3 | 3.9.3 |
References
- https://aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/
- https://github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0ac
- https://github.com/nltk/nltk/pull/3465
- https://github.com/nltk/nltk/releases/tag/3.9.3
- https://www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-line-arguments