Critical Security Update for python3-pyasn1: Denial of Service Vulnerability
Summary
ALSA-2026:59242: Important: python-pyasn1 security update. Affects python3-pyasn1 versions < 0.4.8-7.el9_8.1. Fixed in 0.4.8-7.el9_8.1. 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 various applications that require data serialization and communication protocols. The library supports dynamic typing and high-level data types, making it versatile for developers. However, a recent vulnerability has been identified that could allow attackers to exploit crafted ASN.1 REAL values, leading to a Denial of Service (DoS) condition.
Vulnerability Detail
The vulnerability, identified as CVE-2026-59886, arises from the handling of crafted ASN.1 REAL values within the pyasn1 library. Attackers can exploit this flaw by sending specially crafted inputs that the library fails to process correctly, resulting in a Denial of Service. This could lead to application crashes or unresponsive states, severely impacting the availability of services relying on this library. The issue is particularly concerning for applications that process untrusted input, as it could be exploited remotely.
How To Fix
Minimum fixed version
0.4.8-7.el9_8.1
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
As a temporary measure, you can implement input validation to filter out potentially malicious ASN.1 REAL values before they are processed by the pyasn1 library. This can help mitigate the risk of exploitation until the package is updated.
Conclusion
The python3-pyasn1 library has a critical vulnerability that could lead to Denial of Service attacks. It is crucial to update to the patched version to mitigate risks. Implementing input validation can serve as a temporary measure until the update is applied. For real-time monitoring of open-source vulnerabilities, consider using Vulert, which can alert you to issues without requiring code access.
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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 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 application crashes or unresponsive states, affecting the availability of services that rely on the python3-pyasn1 library.
Yes, a patch is available in version 0.4.8-7.el9_8.1 of the python3-pyasn1 and python3-pyasn1-modules packages.
If you cannot update the package immediately, implement input validation to filter out potentially malicious ASN.1 REAL values as a temporary workaround.
Related vulnerabilities
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