Urgent: Critical Linux Kernel Security Flaws Patched for Ubuntu 16.04 LTS Oracle Cloud Systems (USN-7685-5)

 

 Critical Linux kernel vulnerabilities (CVE-2023-52757 to CVE-2025-37797) threaten Ubuntu 16.04 LTS Oracle Cloud systems. Learn the impacted subsystems (Ext4, SMB, Bluetooth), urgent patching steps via Ubuntu Pro, reboot requirements, and ABI change implications. Secure your infrastructure now!

High-Severity Vulnerabilities Demand Immediate Patching

Multiple critical security vulnerabilities have been identified within the Linux kernel powering Ubuntu 16.04 LTS, specifically impacting systems utilizing the linux-oracle kernel optimized for Oracle Cloud environments (USN-7685-5). 

These flaws, if exploited, present a severe risk of system compromise, unauthorized data access, and potential disruption of critical cloud services. Is your infrastructure protected against the latest zero-day threats targeting core OS components?

Successful exploitation could grant attackers significant privileges, enabling them to bypass security controls, manipulate system operations, or establish persistent access. 

The breadth of affected subsystems underscores the pervasive nature of these threats. Immediate application of the provided kernel updates is non-negotiable for maintaining enterprise-grade security posture and compliance.

Detailed Breakdown of Exploitable Kernel Subsystems

The patched vulnerabilities reside within critical areas of the Linux kernel. Understanding these vectors is essential for risk assessment:

• Device Tree & Open Firmware Drivers: Flaws here could allow attackers to manipulate hardware initialization, a critical early-boot process.

• SCSI Subsystem: Vulnerabilities threaten storage integrity and availability for attached devices.

• TTY Drivers: Exploits could enable control over terminal sessions or facilitate escape mechanisms.

• Ext4 File System: Risks include data corruption, privilege escalation via file operations, or denial-of-service.

• SMB Network File System (CIFS): Critical for network shares; exploits could lead to remote code execution or unauthorized access.

• Bluetooth Subsystem: Proximity-based attacks could compromise devices or intercept data.

• Network Traffic Control (Traffic Shaping/QoS): Manipulation could disrupt network performance or enable denial-of-service.

• Sun RPC Protocol: Underpins NFS; vulnerabilities could compromise network service security.

• USB Sound Devices: Potentially obscure vectors for privilege escalation via peripheral input.

Comprehensive List of Addressed CVEs

This security update resolves the following critical Common Vulnerabilities and Exposures (CVEs), representing a significant hardening of the kernel:

• CVE-2023-52757, CVE-2023-52885, CVE-2023-52975

• CVE-2024-38541, CVE-2024-49883, CVE-2024-49950, CVE-2024-50073, CVE-2024-53239, CVE-2024-56748

• CVE-2025-37797

Referencing these CVE identifiers is crucial for vulnerability management tracking and cross-referencing with security intelligence feeds.

Mandatory Update Instructions for Ubuntu 16.04 LTS Oracle Kernels

Required Package Versions (Exclusively via Ubuntu Pro)

Due to the extended support lifecycle required for legacy LTS releases like 16.04, these critical patches are only accessible through an active Ubuntu Pro subscription. Ensure your systems are attached to an Ubuntu Pro account. Update to the following exact package versions:

1. linux-image-4.15.0-1145-oracle: Version 4.15.0-1145.156~16.04.1

2. linux-image-oracle (Metapackage): Version 4.15.0.1145.156~16.04.1

Critical Post-Update Actions

• System Reboot: A full system reboot is absolutely mandatory after applying these kernel updates. The running kernel cannot be patched live; the new kernel only activates upon restart. Schedule this maintenance window immediately.

• ABI Change & Third-Party Modules (Essential Attention!): This update includes an unavoidable Application Binary Interface (ABI) change, indicated by the new kernel version number. This requires you to:

• Recompile any custom or third-party kernel modules (DKMS modules).

• Reinstall these recompiled modules.

• Standard systems: If you haven't manually removed core metapackages (linux-generic, linux-generic-lts-xenial, linux-virtual, etc.), the update-manager process should handle DKMS recompilation automatically during the upgrade. Verify this process completes successfully in your logs.

• Custom systems: If you manage kernel modules manually or use non-standard configurations, proactive intervention is required to recompile and reinstall modules against the new kernel headers. Failure will result in modules failing to load after reboot, potentially causing hardware or functionality issues.

Why Prompt Patching is a Non-Negotiable Security Imperative

Unpatched kernel vulnerabilities represent the highest risk level in system security. Attackers actively scan for systems missing critical updates like these. The consequences of exploitation extend far beyond a single server:

1. Data Breach: Exfiltration of sensitive customer or corporate data.

2. Service Disruption: Downtime impacting revenue and reputation (Ransomware, DoS).

3. Compliance Violations: Failure to patch critical CVEs often breaches regulations (PCI-DSS, HIPAA, GDPR).

4. Lateral Movement: A compromised system becomes a beachhead for attacking internal networks.

5. Reputational Damage: Public disclosure of a breach due to unpatched systems is devastating.

Leveraging Ubuntu Pro for Extended Security Maintenance (ESM)

Ubuntu 16.04 LTS reached its standard end-of-life (EOL) in April 2021. Ubuntu Pro is the only source for continued security patches, including critical kernel updates like this one, for the full ESM period. 

This subscription is essential for maintaining security and compliance on legacy 16.04 systems still in operation, especially in cloud environments like Oracle Cloud where uptime is paramount.

Official References & Vulnerability Details

• Ubuntu Security Notice (USN) Primary: https://ubuntu.com/security/notices/USN-7685-5

• Related USNs (for context/completeness):

  • https://ubuntu.com/security/notices/USN-7685-4

  • https://ubuntu.com/security/notices/USN-7685-3

  • https://ubuntu.com/security/notices/USN-7685-2

  • https://ubuntu.com/security/notices/USN-7685-1

• Ubuntu Pro Information: https://ubuntu.com/pro

• CVE Details: Search the listed CVE IDs (e.g., CVE-2023-52757) on the National Vulnerability Database (NVD) for in-depth technical analysis and severity scores.

Frequently Asked Questions (FAQ)

• Q: My Ubuntu 16.04 system isn't on Oracle Cloud. Am I affected?

• A: This specific USN (USN-7685-5) addresses the linux-oracle kernel variant. If you are using a different kernel flavor (e.g., linux-generic), check other USNs (like USN-7685-1 to USN-7685-4). All Ubuntu 16.04 LTS systems require kernel updates, but the exact package depends on the kernel variant installed.

• Q: I don't have Ubuntu Pro. Can I get this patch?

• A: No. Critical security updates for Ubuntu 16.04 LTS after its standard EOL are exclusively delivered through Ubuntu Pro subscriptions. Upgrading to a supported release (22.04 LTS or 24.04 LTS) is the alternative.

• Q: What happens if I don't recompile third-party modules?

• A: After reboot, any hardware or functionality relying on those un-recompiled modules will likely fail (e.g., specialized drivers, VPN software, storage controllers). This can render a system unusable or unstable.

• Q: How critical are these vulnerabilities?

• A: Extremely critical. They affect core kernel subsystems, and exploits could lead to full system compromise. Patching is urgent.

• Q: Can I mitigate these without patching?

  • A: While strict network controls and limiting attack surface help, patching is the only definitive mitigation for these specific code flaws. Relying solely on workarounds is high-risk.

Proactive Security: The Only Defense

The discovery of these vulnerabilities highlights the relentless nature of cyber threats targeting foundational infrastructure like the Linux kernel.

 Proactive patch management, utilizing extended support programs like Ubuntu Pro for legacy systems, and rigorous system hardening are not best practices—they are survival necessities in today's threat landscape. Don't let your Ubuntu 16.04 LTS Oracle Cloud systems become the weakest link.

Action: Log in to your Ubuntu Pro dashboard immediately, ensure your 16.04 LTS Oracle Cloud systems are attached and covered, and apply these critical kernel updates. Schedule the mandatory reboot and verify third-party module compatibility before maintenance. Your system's integrity depends on it.