Critical Linux Kernel Real-Time Vulnerabilities Patched: Update Now (USN-7609-2 Security Advisory)

 

Ubuntu has released USN-7609-2 to patch critical Linux kernel real-time vulnerabilities affecting InfiniBand, Netfilter, and traffic control subsystems. Learn how to update, mitigate risks, and secure systems with Ubuntu Pro’s 10-year coverage.

Urgent Security Update: Linux Kernel Real-Time Flaws Expose Systems to Attacks

Published: July 1, 2025

The Ubuntu Security Team has issued USN-7609-2, addressing multiple high-severity vulnerabilities in the Linux kernel real-time (RT) variants, including Raspberry Pi deployments.

These flaws could allow privilege escalation, denial-of-service (DoS), or remote code execution if unpatched.

Affected Packages

• linux-realtime: Linux kernel for real-time systems

• linux-raspi-realtime: Linux kernel for Raspberry Pi real-time systems

Key Vulnerabilities Patched:

• CVE-2025-38001/38000: Netfilter bypass exploits (critical for cloud workloads)

• CVE-2025-37997: InfiniBand driver memory corruption (high-risk for HPC clusters)

• CVE-2025-37890: Traffic control subsystem privilege escalation

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How to Update Your Linux Real-Time Kernel

Step-by-Step Patch Instructions

1. Run a standard system update:

   bash

   sudo apt update && sudo apt upgrade

2. Reboot your system to activate the new kernel.

3. Recompile third-party modules: Due to an ABI change, manually reinstall kernel modules (e.g., DKMS drivers).

⚠️ Warning: Systems using custom kernel modules (e.g., NVIDIA drivers, ZFS) must rebuild them post-update.

Package Versions for Ubuntu 24.04 (Noble):

Package	Version
linux-image-6.8.0-2025-raspi-realtime	6.8.0-2025.26
linux-image-realtime-6.8.1	6.8.1-1024.25

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Mitigation Strategies for Enterprise Users

1. Reduce Exposure with Ubuntu Pro

• Free for 5 machines: Extend security coverage to 25,000+ packages for 10 years.

• Priority CVE patches: Get fixes for zero-day exploits before standard releases.

👉 Get Ubuntu Pro Now

2. Hardening Recommendations

• Disable unused kernel modules (e.g., modprobe -r).

• Implement network segmentation for InfiniBand deployments.

• Monitor dmesg logs for Netfilter anomalies.

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Technical Deep Dive: Impacted Subsystems

1. Netfilter Vulnerabilities (CVE-2025-38001)

The Linux kernel’s firewall stack had boundary condition flaws, allowing attackers to bypass rulesets. Affects:

• Cloud-native workloads

• Kubernetes nodes using iptables

2. InfiniBand Driver Risks (CVE-2025-37997)

A race condition in RDMA drivers could leak kernel memory. Critical for:

• High-performance computing (HPC)

• AI/ML clusters leveraging RDMA

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FAQs: Linux Kernel Real-Time Patches

Q: Do I need to reboot after updating?

A: Yes. Kernel updates require a reboot to load the patched version.

Q: How do I check my current kernel version?

A: Run uname -r in the terminal.

Q: Is Ubuntu Pro mandatory for fixes?

A: No, but it provides long-term support beyond standard EOL dates.