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🛡️ CVE-2025-71408 — nltk

🟠 CVSS 8.0 — High ⚠️ Exploit Public CWE-95 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

NLTK vulnerable to Eval Injection via collocations CLI arguments

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.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: 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

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Attack requirements: None — no deployment-specific condition has to hold.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2025-71408 is classified as CWE-95: Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection'). The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before using the input in a dynamic evaluation call (e.g. "eval").

Affected software

CVE-2025-71408 is recorded against 1 package.

  • nltk (fixed in 3.9.3)

Timeline and source

Published on 25 July 2026 and last revised on 19 August 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from OSV.

References

nvd.nist.gov (Advisory)
github.com (Web)
github.com (Web)
aydinnyunus.github.io (Web)
github.com (Package)
github.com (Web)
github.com (Web)
www.vulncheck.com (Web)

Other advisories for this package

nltk has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-95: Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')) in other software:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector 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
CWE CWE-95
Public Exploit ⚠️ Yes
Source OSV
Published 2026-07-25
Updated 2026-08-20
Modified 2026-08-19

Affected Packages

Software From version Fixed in
nltk — 3.9.3

Similar Threats

Exploit Protection

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CVE-2025-71408 carries CVSS 8.0 High rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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