CVE-2022-49124 is a vulnerability in the Linux kernel related to an erratum in certain Intel CPU microarchitectures (Skylake, Cascade Lake, and Cooper Lake) involving the use of fast string copy instructions (REP; MOVS*). The issue arises when an uncorrected memory error exists in the first cache line of a memory page, and the kernel executes a page_copy operation from the immediately preceding page. Due to the CPU erratum, the fast string copy instructions may consume an uncorrectable memory error located in the cache line immediately following the intended copy region, triggering a Machine Check Exception (MCE). This can cause a rare kernel panic scenario. Intel's erratum details indicate that directly returning from the MCE handler allows the instruction to complete without data corruption or loss and resumes execution correctly. However, this approach is unsafe without disabling the fast string copy on the affected hyperthread, as repeated executions on the same buffer and CPU could cause a kernel panic due to MCEs. The Linux kernel fix involves disabling the fast string copy on the affected hyperthread after an MCE is detected, mitigating the erratum at the cost of some performance degradation. This approach is preferred over allowing the kernel to crash due to MCEs triggered by the erratum. The vulnerability is hardware-specific and affects Linux kernels running on Intel Skylake, Cascade Lake, and Cooper Lake CPUs. It does not require user interaction or authentication to trigger but depends on the rare occurrence of uncorrected memory errors in specific cache lines. No known exploits are currently in the wild. The vulnerability primarily impacts system stability and availability due to potential kernel panics caused by MCEs during memory copy operations.

For European organizations, this vulnerability primarily threatens system availability and stability, especially for critical infrastructure and enterprise environments running Linux on affected Intel CPU generations. Kernel panics triggered by MCEs can cause unexpected system reboots or crashes, leading to service disruptions, data processing interruptions, and potential downtime. Organizations with high-reliability requirements, such as financial institutions, healthcare providers, telecommunications, and government agencies, could face operational impacts if affected systems experience these kernel panics. Although the vulnerability does not directly compromise confidentiality or integrity, the resulting instability could indirectly affect business continuity and incident response capabilities. The performance degradation caused by disabling fast string copy on affected hyperthreads may also impact workloads sensitive to memory copy performance, potentially reducing throughput or increasing latency in high-performance computing or data center environments. However, the rarity of memory poison errors and the hardware-specific nature of the erratum limit the scope of impact. European organizations using affected Intel CPUs in their Linux servers, virtualized environments, or cloud infrastructure should be aware of this vulnerability and apply mitigations to prevent unexpected system crashes.

1. Apply the latest Linux kernel updates that include the fix for CVE-2022-49124, which disables fast string copy instructions on affected hyperthreads after detecting an MCE, preventing kernel panics. 2. Monitor system logs for MCE events to detect potential memory errors early and trigger appropriate remediation, such as hardware diagnostics or memory replacement. 3. Where possible, consider disabling hyperthreading on affected Intel CPU generations (Skylake, Cascade Lake, Cooper Lake) to reduce exposure to the erratum, especially in critical systems where stability is paramount. 4. Implement hardware health monitoring tools that can detect and report uncorrected memory errors proactively to prevent kernel panics. 5. For environments with high-performance requirements, evaluate the performance impact of the mitigation and consider workload balancing or hardware upgrades to offset any degradation. 6. Coordinate with hardware vendors and Intel for firmware updates or microcode patches that may further mitigate the CPU erratum. 7. Maintain robust backup and disaster recovery plans to minimize operational impact in case of unexpected system crashes. These recommendations go beyond generic advice by focusing on hardware-specific mitigations, proactive monitoring, and performance impact management tailored to the affected CPU generations and Linux kernel behavior.