CVE-2025-71408: Nltk code injection (CVSS 7.8)

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.

CVSS 3.1 breakdown

Attack vectorLocal

Attack complexityLow

Privileges requiredLow

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Affected products

Nltk< 3.9.3

Remediation

Fixed in

Nltk≥ 3.9.3

Patch & vendor advisories

References

https://aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/ExploitPress/Media CoverageThird Party Advisory
https://github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0acPatch
https://github.com/nltk/nltk/pull/3465Issue TrackingPatch
https://github.com/nltk/nltk/releases/tag/3.9.3Release Notes
https://www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-line-argumentsPatchThird Party Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2025-71408 being actively exploited?

CVE-2025-71408 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.27%.

How severe is CVE-2025-71408?

CVE-2025-71408 has a CVSS 3.1 base score of 7.8, rated high. EPSS estimates a 0.27% probability of exploitation.

Which products are affected by CVE-2025-71408?

Affected products include Nltk.

How do I fix CVE-2025-71408?

Upgrade affected software to a fixed version, for example Nltk 3.9.3 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-71408 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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