Infinite Loop Vulnerability in Python Rencode Package: CVE-2021-40839
Summary
UBUNTU-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 1.0.3-1build1 – 1.0.3-1build2. No fix is published. How to fix ↓
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Background
The rencode package is a Python library used for encoding and decoding data structures. It is designed to provide efficient serialization for Python objects. However, versions up to 1.0.6 have been found to contain a vulnerability that allows for an infinite loop during typecode decoding, which can lead to excessive CPU and memory consumption.
Vulnerability Detail
The vulnerability identified as CVE-2021-40839 exists in the rencode package through version 1.0.6. It allows attackers to exploit the decoding process, particularly through crafted input such as ';\x2f\x7f'. This can lead to an infinite loop, consuming system resources and potentially causing denial of service. The vulnerability is classified with a CVSS score of 7.5, indicating a high severity level.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, users can avoid using the rencode package until the package is updated to a secure version. Additionally, input validation can be implemented to filter out potentially malicious inputs that could trigger the infinite loop.
Conclusion
The rencode package has a critical vulnerability that can lead to resource exhaustion through an infinite loop during decoding. It is essential for users to update to the latest patched versions to mitigate this risk. Temporary workarounds can be employed until updates are applied.
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FAQ
CVE-2021-40839 is a vulnerability in the rencode package that allows for an infinite loop during typecode decoding, leading to resource exhaustion.
Versions of the rencode package up to 1.0.6 are affected by this vulnerability.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
If you cannot update the package, consider implementing input validation to mitigate the risk of exploitation.
The CVSS score of CVE-2021-40839 is 7.5, indicating a high severity level.
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