Critical glibc Vulnerability in AlmaLinux: Information Disclosure and Denial of Service
Summary
ALSA-2026:42952: Moderate: glibc security update. Affects glibc versions < 2.34-274.el9_8. Fixed in 2.34-274.el9_8. How to fix ↓
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Background
The GNU C Library (glibc) is a core component of the Linux operating system, providing essential functionalities such as standard C libraries, POSIX thread libraries, and standard math libraries. It is crucial for the operation of various applications and services on the system. This vulnerability affects glibc versions prior to 2.34-274.el9_8, which may lead to serious security risks.
Vulnerability Detail
The vulnerability arises from improper handling of specific wide character encodings in the ungetwc function, which can lead to information disclosure or denial of service (CVE-2026-5928). Additionally, an out-of-bounds write can occur during TSIG record processing (CVE-2026-5435), and crafted DNS responses can cause application crashes or uninitialized memory reads (CVE-2026-6238). These vulnerabilities can be exploited by attackers to compromise system integrity and availability.
How To Fix
Minimum fixed version
2.34-274.el9_8
This is the first release that contains the fix.
sudo dnf update glibcTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, consider disabling the affected services or applications that rely on glibc until the update can be applied. This may help mitigate the risk of exploitation until a full patch is implemented.
Conclusion
The glibc vulnerability poses significant risks to systems running affected versions. It is crucial to apply the necessary updates to mitigate these risks and ensure system integrity. Regular monitoring and prompt action are essential to maintain security.
See every vulnerability recorded for glibc →
FAQ
glibc, or the GNU C Library, is a standard library for the C programming language that provides essential functionalities for Linux applications.
The risks include potential information disclosure, denial of service, application crashes, and exploitation of uninitialized memory, which can lead to system compromise.
You can check your system's glibc version using the command 'rpm -q glibc'. If it is below 2.34-274.el9_8, your system is vulnerable.
Yes, you can use Vulert, which monitors and alerts for open-source vulnerabilities in your software using just a manifest file like package-lock.json. You can check your application for vulnerabilities without signup at the Vulert playground.
If an immediate update is not possible, consider disabling affected services or applications as a temporary measure to reduce risk.
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