The Unbreakable Enterprise Kernel (UEK) for Oracle Linux provides the latest open source innovations and key optimizations and security to enterprise cloud and on-premises workloads. It is the Linux kernel that powers Oracle Cloud and Oracle Engineered Systems such as Oracle Exadata Database Machine as well as Oracle Linux on 64-bit Intel and AMD or 64-bit Arm platforms.
The Unbreakable Enterprise Kernel Release 5 Update 4 (UEK R5U4) is based on the mainline kernel version 4.14.35. Through actively monitoring upstream check-ins and collaboration with partners and customers, Oracle continues to improve and apply critical bug and security fixes to UEK R5 for Oracle Linux. This update includes several new features, added functionality, and bug fixes across a range of subsystems.
UEK R5 Update 4 can be recognized with a release number starting with 4.14.35-2025.400.8.
- Core Kernel Functionality. UEK R5U4 provides equivalent core kernel functionality to UEK R5U3 and older, making use of the same upstream mainline kernel release, with additional patches to enhance existing functionality and provide some minor bug fixes and security improvements.
- Process Virtual Address Space Reservation. Process Virtual Address Space Reservation allows reservation of process virtual address ranges; This feature is specifically developed to improve Oracle Database stability when ASLR (Address Space Layout Randomization) is enabled.
- File system and storage fixes.
- NFS. NFS is updated with several upstream fixes, along with improvements and optimizations for page cache, RPC call handling and NFSv4 clients.
- OCFS2. Issues with NFS kernel server when hosted on OCSF2 filesystem are resolved
- Networking. UEK R5U4 supports 1/10/25/50/100 Gb Ethernet ports. 200 Gb Ethernet ports are not enabled in UEK R5U4 as the changes required to support this affect the kernel ABI. If you require the use of 200 Gb Ethernet ports use UEK R6.
- Enhanced TCP Stack for diagnostics. Enhancements are added to the tcp stack to facilitate better diagnostics through extended Berkeley Packet Filter (eBPF) tracepoints along with several optimizations that allow more rapid diagnostics and testing, but also to reduce performance overhead related to tracing.
- Spectre-v1 mitigation extensions. Patches available in the upstream Linux 5.6 kernel are included to extend Spectre-v1 mitigation by preventing index computations from causing speculative loads into the L1 cache.
- Driver Updates. UEK R5 supports a large number of hardware and devices. In close cooperation with hardware and storage vendors, Oracle has updated several device drivers from the versions in mainline Linux 4.14.35. Further details are available on section “1.2.1 Notable Driver Features and Updates” of the Release Notes.
For more details on these and other new features and changes, please consult the Release Notes for the UEK R5 Update 4.
Security (CVE) Fixes
Supported Upgrade Path
Oracle Linux can be downloaded, used, and distributed free of charge and all updates and errata are freely available. This allows organizations to decide which systems require a support subscription and makes Oracle Linux an ideal choice for development, testing, and production systems. The user decides which support coverage is the best for each system individually, while keeping all systems up-to-date and secure. Customers with Oracle Linux Premier Support also receive access to zero-downtime kernel updates using Oracle Ksplice.
UEK R5 Update 4 is fully compatible with the UEK R5 GA release. The kernel ABI for UEK R5 remains unchanged in all subsequent updates to the initial release.
About Oracle Linux
Oracle Linux is an open and complete operating environment that helps accelerate digital transformation. It delivers leading performance and security for hybrid and multi cloud deployments. Oracle Linux is 100% application binary compatible with Red Hat Enterprise Linux. And, with an Oracle Linux Support subscription, customers have access to award-winning Oracle support resources and Linux support specialists, zero-downtime patching with Ksplice, cloud native tools such as Kubernetes and Kata Containers, KVM virtualization and oVirt-based virtualization manager, DTrace, clustering tools, Spacewalk, Oracle Enterprise Manager, and lifetime support. All this and more is included in a single cost-effective support offering. Unlike many other commercial Linux distributions, Oracle Linux is easy to download and completely free to use, distribute, and update.