Critical Rocky Linux 8 kernel-rt security update RLSA-2025:13590 patches multiple high-severity vulnerabilities, including CVE-2025-21727 and CVE-2025-38159. Learn about the risks, patched CVEs, and how to immediately update your kernel packages to prevent potential system compromise.
A new security advisory, RLSA-2025:13590, has been issued for the real-time (kernel-rt) kernel packages on Rocky Linux 8. This is not a routine update; it addresses multiple critical Common Vulnerabilities and Exposures (CVEs) that could potentially allow attackers to compromise system stability, escalate privileges, or cause denial-of-service conditions.
For system administrators and DevOps professionals managing enterprise-grade Rocky Linux deployments, applying this patch is not just recommended—it's imperative for maintaining a secure infrastructure posture.
This comprehensive analysis will break down the RLSA-2025:13590 advisory, detailing the specific vulnerabilities, their potential impact on your Rocky Linux 8 environments, and providing a clear, actionable guide to remediation.
We will delve into the technical specifics of each CVE to help you assess risk and prioritize your update cycles effectively.
Understanding the Security Risks: A Breakdown of the Patched CVEs
The kernel is the core of any operating system, controlling everything from hardware interaction to process scheduling.
The real-time kernel variant is often deployed in sensitive, high-performance computing environments where stability and predictable latency are non-negotiable. The vulnerabilities patched in this update, therefore, pose a significant threat to these critical workloads.
The update specifically addresses the following five CVEs. Each has been assigned a Common Vulnerability Scoring System (CVSS) score, providing a standardized measure of severity.
CVE-2025-21727: A vulnerability discovered in the Linux kernel's memory management subsystem. This flaw could allow a local attacker to trigger a use-after-free condition, potentially leading to a system crash or arbitrary code execution with elevated privileges.
CVE-2025-21759: This CVE pertains to an issue within the kernel's networking stack. Exploitation could enable a remote attacker to send specially crafted packets, resulting in a denial-of-service (DoS) state, crippling network services on the affected machine.
CVE-2025-38085 & CVE-2025-38159: These are two distinct vulnerabilities related to filesystem handling and device driver interactions, respectively. Successful exploitation could lead to information disclosure or kernel panic, undermining both data confidentiality and system availability.
CVE-2021-47670: This is an older vulnerability that is being backported into this patch set, highlighting Rocky Linux's commitment to comprehensive security maintenance, ensuring even previously disclosed issues are fully addressed in its long-term support branches.
Why should enterprise environments treat kernel updates with the highest priority? Unlike application-level bugs, a kernel-level exploit can bypass nearly all security boundaries, granting an attacker near-total control over the system. The risks range from data breaches to complete service outage.
Affected Packages and Remediation Steps
The advisory affects a suite of kernel-rt packages for the x86_64 architecture. The complete list of updated RPMs includes:
| Package Name | Version | Release | Architecture |
|---|---|---|---|
kernel-rt | 4.18.0 | 553.69.1.rt7.410.el8_10 | x86_64 |
kernel-rt-core | 4.18.0 | 553.69.1.rt7.410.el8_10 | x86_64 |
kernel-rt-devel | 4.18.0 | 553.69.1.rt7.410.el8_10 | x86_64 |
kernel-rt-modules | 4.18.0 | 553.69.1.rt7.410.el8_10 | x86_64 |
| (and others listed in the advisory) |
How to Apply the Kernel Security Patch
Applying the update is a straightforward process using the dnf package manager, which will handle dependencies and package retrieval automatically. The following commands will update your system.
First, update your package repository cache:
sudo dnf check-updateApply the security update specifically for the kernel-rt packages:
sudo dnf update kernel-rtImportant: A kernel update requires a system reboot to load the new, patched kernel into memory.
sudo reboot
Pro Tip: For high-availability systems where an immediate reboot is not feasible, consider using live kernel patching solutions like kpatch if available and supported for your specific kernel version and environment. However, a reboot remains the most reliable method to ensure the patch is fully active.
Best Practices for Enterprise Linux Security Maintenance
Beyond applying this immediate patch, adhering to a rigorous security hygiene protocol is essential. This includes:
Subscribing to Security Advisories: Regularly monitor official channels like the Rocky Linux Announcements mailing list for immediate notifications.
Scheduled Update Cycles: Establish a regular, tested patch cycle for your development, staging, and production environments to minimize exposure windows without sacrificing stability.
Vulnerability Scanning: Utilize tools like Tenable Nessus or OpenVAS to automatically scan your infrastructure for unpatched systems and known vulnerabilities.
Configuration Management: Use tools like Ansible, Puppet, or Chef to automate the deployment of security patches across your entire server fleet, ensuring consistency and reducing human error.
Conclusion and Key Takeaways
The RLSA-2025:13590 kernel-rt security update is a critical response to actively documented vulnerabilities that threaten the integrity of Rocky Linux 8 systems. The patched flaws, including CVE-2025-21727 and CVE-2025-38159, underscore the persistent need for vigilant security maintenance at the kernel level.
System administrators must prioritize applying this patch, followed by a necessary reboot, to mitigate risks of privilege escalation, denial-of-service attacks, and potential system compromise. Maintaining an up-to-date system is the most fundamental and effective defense against evolving cyber threats targeting core operating system components.
Your next step: Log into your Rocky Linux 8 systems now and execute the update commands. Schedule necessary reboots during your next maintenance window to ensure your infrastructure remains secure, stable, and performant.
Frequently Asked Questions (FAQ)
Q1: What is Rocky Linux RLSA-2025:13590?
A: RLSA-2025:13590 is an official security advisory from the Rocky Linux team detailing a security update for the real-time (kernel-rt) kernel that patches multiple critical vulnerabilities affecting Rocky Linux 8.
Q2: Do I need to reboot after applying the kernel update?
A: Yes, a system reboot is absolutely required to unload the old vulnerable kernel from memory and load the new, patched version. The update is not active until the system is rebooted.
Q3: Is only the main kernel-rt package affected?
A: No, the advisory affects multiple related packages including kernel-rt-devel, kernel-rt-modules, and kernel-rt-core. It is best to update the entire suite using the command sudo dnf update kernel-rt.
Q4: Where can I find the official CVE details?
A: You can follow the links provided in the advisory to the Mitre CVE database (e.g., https://cve.mitre.org) for in-depth technical descriptions of each vulnerability.
Q5: How does this update impact my containerized workloads?
A: Containers share the host machine's kernel. Therefore, patching the host system's kernel is essential to protect both the host and all containers running on it from kernel-level exploits.
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