CVE-2026-33230: NLTK WordNet App Reflected XSS Vulnerability
Summary
CVE-2026-33230: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in nltk. Affects nltk versions < 3.9.3. No fix is published. How to fix ↓
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Background
The Natural Language Toolkit (NLTK) is a powerful library in Python used for working with human language data (text). It provides easy-to-use interfaces to over 50 corpora and lexical resources, along with a suite of text processing libraries for classification, tokenization, stemming, tagging, parsing, and more. The NLTK WordNet App allows users to browse the WordNet lexical database through a web interface. However, it has a vulnerability that allows for reflected cross-site scripting (XSS) attacks, which can compromise the security of users running the application locally.
Vulnerability Detail
The vulnerability arises from improper neutralization of input during web page generation in the NLTK WordNet App. Specifically, the 'lookup_' route allows attacker-controlled data to be reflected into HTML without proper escaping. This can lead to arbitrary HTML/JavaScript being injected into the response page, enabling an attacker to execute scripts in the context of the user's browser. The vulnerability is exploitable due to the handling of base64-encoded pickle data, which can be manipulated to inject malicious scripts. This poses a risk to users who run the WordNet Browser server locally, as it can lead to unauthorized actions and data exposure.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, avoid using the 'lookup_' route in the NLTK WordNet App until the package is updated. Additionally, consider running the application in a controlled environment where access is restricted to trusted users only.
Conclusion
The NLTK WordNet App has a reflected XSS vulnerability that can be exploited by attackers to execute scripts in the context of users' browsers. It is crucial for users to update their NLTK package to mitigate this risk and to be cautious when using the application until the update is applied.
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FAQ
CVE-2026-33230 is a vulnerability in the NLTK WordNet App that allows for reflected cross-site scripting (XSS) attacks.
Users running the NLTK WordNet App locally can be exposed to XSS attacks, allowing attackers to execute arbitrary scripts in their browsers.
You should update your NLTK package to the latest version that fixes the vulnerability. Use 'pip install --upgrade nltk' to do so.
Yes, you can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without any signup.
The CVSS score of this vulnerability is 6.1, indicating a moderate level of severity.
References
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