Inefficient Regular Expression Complexity in NLTK: CVE-2021-3842
Summary
CVE-2021-3842: nltk is vulnerable to Inefficient Regular Expression Complexity. Affects nltk versions < 2a50a3edc9d35f57ae42a921c621edc160877f4d. No fix is published. How to fix ↓
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Background
NLTK (Natural Language Toolkit) 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 vulnerability CVE-2021-3842 affects NLTK's handling of regular expressions, potentially leading to performance issues when processing certain inputs.
Vulnerability Detail
CVE-2021-3842 is a vulnerability in the NLTK library that arises from inefficient regular expression complexity. This can lead to Denial of Service (DoS) conditions, where an attacker can craft specific inputs that cause excessive resource consumption, slowing down or crashing the application. The vulnerability is present in all versions of NLTK prior to the fix, which was introduced in version 3.6.7-1 for Debian packages and commit 2a50a3edc9d35f57ae42a921c621edc160877f4d in the Git repository.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
If immediate upgrading is not possible, consider limiting the input size or sanitizing inputs to avoid triggering the inefficient regular expressions. Implementing input validation can help mitigate the risk until an upgrade can be performed.
Conclusion
CVE-2021-3842 is a significant vulnerability affecting the NLTK library, which can lead to performance degradation and potential Denial of Service. It is crucial for users to update their NLTK installations to the latest version to mitigate this risk. Utilizing tools like Vulert can help in monitoring and managing vulnerabilities effectively.
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FAQ
CVE-2021-3842 is a vulnerability in the NLTK library that involves inefficient regular expression complexity, potentially leading to performance issues.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
The vulnerability can lead to Denial of Service (DoS) conditions, where an attacker can exploit the inefficient regex to consume excessive resources.
You can update NLTK by running the command 'pip install --upgrade nltk' in your terminal.
Vulert is a tool that monitors and alerts for open-source vulnerabilities in software using just a manifest file like package-lock.json.
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