nltk/nltk: Improper Control of Generation of Code
CVE-2025-14009 is a high-severity improper control of generation of code vulnerability in nltk/nltk from Nltk, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected nltk/nltk versions: latest and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.02% chance of exploitation within 30 days, higher than 64% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Nltk to 3.9.3 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Nltk | nltk/nltk | latest and earlier | Not stated |
| Red Hat | Red Hat OpenShift AI 2.25 | Not specified in the record | Not stated |
| Red Hat | OpenShift Lightspeed | Not specified in the record | Not stated |
| Red Hat | Red Hat OpenShift AI (RHOAI) | Not specified in the record | Not stated |
| Nltk | Nltk | before 3.9.3 | 3.9.3 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | CNA |
| CVSS 3.0 | 10.0 | Critical | CNA (huntr.dev) |
Official description
A critical vulnerability exists in the NLTK downloader component of nltk/nltk, affecting all versions. The _unzip_iter function in nltk/downloader.py uses zipfile.extractall() without performing path validation or security checks. This allows attackers to craft malicious zip packages that, when downloaded and extracted by NLTK, can execute arbitrary code. The vulnerability arises because NLTK assumes all downloaded packages are trusted and extracts them without validation. If a malicious package contains Python files, such as __init__.py, these files are executed automatically upon import, leading to remote code execution. This issue can result in full system compromise, including file system access, network access, and potential persistence mechanisms.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Control of Generation of Code
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
How developers prevent this class of flaw
- Refactor your program so that you do not have to dynamically generate code.
- Run your code in a jail or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which code can be executed by your product. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
- Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
More Improper Control of Generation of Code vulnerabilities (CWE-94)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Technical write-ups (may include proof of concept)
- huntr.com/bounties/49ecbc02-054e-4470-b2e0-b267936cc4e4Exploit, Third Party Advisory
Other references
Other vulnerabilities in nltk/nltk
- 7.8 High severity
- 7.5 High severity
- 7.5 High severity
- 10.0 Critical severity
- 7.5 High severity
Recent Improper Control of Generation of Code vulnerabilities
- 9.1 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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