Critical Vulnerability in python3-pyasn1: Denial of Service via ASN.1 REAL Values
Summary
ALSA-2026:59241: Important: python-pyasn1 security update. Affects python3-pyasn1 versions < 0.3.7-6.el8_10.2. Fixed in 0.3.7-6.el8_10.2. How to fix ↓
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Background
Python3-pyasn1 is a library for encoding and decoding ASN.1 data structures in Python. It is widely used in applications that require data serialization and communication protocols. The library supports various data types and structures, making it essential for developers working with network protocols and data interchange formats. However, a recent vulnerability has been identified that could allow attackers to exploit the library, leading to potential service disruptions.
Vulnerability Detail
The vulnerability identified as CVE-2026-59886 allows for a Denial of Service (DoS) attack through the manipulation of crafted ASN.1 REAL values. This issue arises from improper handling of these values, which can lead to excessive resource consumption or application crashes. Attackers can exploit this vulnerability by sending specially crafted data to applications that utilize the python3-pyasn1 library, potentially rendering the application unresponsive and affecting its availability.
How To Fix
Minimum fixed version
0.3.7-6.el8_10.2
This is the first release that contains the fix.
sudo dnf update python3-pyasn1Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If immediate patching is not feasible, consider implementing input validation to filter out potentially harmful ASN.1 REAL values. This can help reduce the risk of exploitation until the package can be updated.
Conclusion
The python3-pyasn1 library has a critical vulnerability that could lead to Denial of Service attacks. It is essential for users of this library to update to the latest patched versions to ensure the security and availability of their applications. Additionally, utilizing tools like Vulert can help monitor and alert for open-source vulnerabilities in real-time.
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FAQ
CVE-2026-59886 is a vulnerability in the python3-pyasn1 library that allows for Denial of Service attacks via crafted ASN.1 REAL values.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
Exploitation of this vulnerability can lead to Denial of Service, causing applications to become unresponsive and affecting their availability.
You can update the packages using the commands: 'sudo dnf update python3-pyasn1' and 'sudo dnf update python3-pyasn1-modules'.
Yes, implementing input validation to filter out harmful ASN.1 REAL values can help mitigate the risk until the packages are updated.
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