Infinite Loop Vulnerability in Python Rencode Package
Summary
DEBIAN-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 < 1.0.6-2. Fixed in 1.0.6-2. 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 widely used in applications that require serialization of complex data types. However, versions of rencode up to 1.0.6 are vulnerable to a specific issue that allows for an infinite loop during typecode decoding, which can lead to significant resource consumption.
Vulnerability Detail
The vulnerability arises from the way the rencode package handles typecode decoding. Specifically, it allows for an infinite loop when processing certain inputs, such as ';\x2f\x7f'. This can be exploited by remote attackers to consume excessive CPU and memory resources, potentially leading to denial of service conditions. The issue is present in all versions of rencode up to 1.0.6, making it critical for users to address this vulnerability promptly.
How To Fix
Minimum fixed version
1.0.6-2
This is the first release that contains the fix.
sudo apt-get install --only-upgrade python-rencodeTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can limit the input data to the rencode package to avoid triggering the infinite loop. This can be done by validating and sanitizing inputs before passing them to the rencode functions.
Conclusion
The rencode package has a critical vulnerability that allows for an infinite loop during typecode decoding, which can be exploited by attackers. Users are strongly advised to update to the patched version to protect their applications from potential denial of service attacks. Implementing input validation can serve as a temporary measure until the update is applied.
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FAQ
The rencode package is used for encoding and decoding Python data structures, making it useful for serialization tasks.
Exploitation of this vulnerability can lead to excessive CPU and memory usage, potentially causing your application to become unresponsive.
Yes, the vulnerability has been patched in version 1.0.6-2 of the rencode package.
You can implement input validation and sanitization as a temporary workaround to mitigate the risk.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software. You can check your application using the Vulert playground without any signup.
References
Related vulnerabilities
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