Infinite Loop Vulnerability in Python rencode Package: CVE-2021-40839
Summary
CVE-2021-40839: The rencode package through 1.0.6 for Python allows an infinite loop in typecode decoding (such as via ;\x2f\x7f), enabling a remote attack that consumes CPU and memory. Affects python-rencode versions < 572ff74586d9b1daab904c6f7f7009ce0143bb75. No fix is published. How to fix ↓
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Background
The rencode package is a Python library designed for efficient encoding and decoding of data structures. It is commonly used for serialization, allowing Python objects to be converted into a format that can be easily stored or transmitted. The package is known for its performance and simplicity, making it a popular choice among developers. However, a critical vulnerability has been identified that allows for an infinite loop during typecode decoding, which can lead to significant resource consumption.
Vulnerability Detail
CVE-2021-40839 is a vulnerability found in the rencode package versions up to 1.0.6. It allows an attacker to exploit typecode decoding, specifically through crafted input such as ';\x2f\x7f'. This can trigger an infinite loop, leading to excessive CPU and memory usage. The vulnerability poses a risk of denial-of-service attacks, where legitimate users may be unable to access services due to resource exhaustion. The issue originates from improper handling of specific input types, making it critical for developers to address.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
If immediate updating is not feasible, consider implementing input validation to sanitize and restrict the typecode inputs processed by the rencode package. This can help mitigate the risk of triggering the infinite loop. Additionally, monitor system resources to detect unusual spikes in CPU and memory usage.
Conclusion
CVE-2021-40839 represents a significant risk for applications using the rencode package, allowing for potential denial-of-service attacks through an infinite loop vulnerability. It is crucial for developers to update to the latest version of the package and consider implementing additional safeguards to protect their applications.
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FAQ
CVE-2021-40839 is a vulnerability in the rencode package that allows for an infinite loop during typecode decoding, potentially leading to denial-of-service attacks.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities. Check your application against CVE-2021-40839 using the Vulert playground at Vulert Scanner.
The vulnerability can lead to excessive CPU and memory consumption, resulting in denial-of-service conditions where legitimate users cannot access the affected service.
Yes, updating to version 1.0.6-2 or later will resolve the vulnerability and ensure that your application is secure.
Implement input validation to sanitize typecode inputs and monitor system resources for unusual activity until you can apply the update.
References
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