CVE-2024-48876 is a vulnerability identified in the Linux kernel related to the stack depot subsystem, specifically the function stack_depot_save_flags(). This function is designed to save stack traces and is intended to be callable from Non-Maskable Interrupt (NMI) context when the STACK_DEPOT_FLAG_CAN_ALLOC flag is unset. However, the vulnerability arises because the function attempts to acquire a spinlock (pool_lock) even in NMI context, which can lead to a deadlock scenario. NMIs are high-priority interrupts that cannot be masked, and if an NMI occurs while the pool_lock is already held by the kernel, the attempt to acquire the same lock again in the NMI handler causes the system to deadlock. The fix involves modifying stack_depot_save_flags() to avoid acquiring the pool_lock in NMI context and instead give up if the lock is not immediately available. Additionally, the documentation has been updated to clarify the intended usage and behavior of this function in NMI context. This vulnerability is a kernel-level concurrency issue that can cause system hangs or freezes due to deadlock conditions triggered by NMIs during lock contention. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet. The affected versions are specific Linux kernel commits identified by their hashes, indicating this is a recent and targeted fix in the kernel source.

For European organizations, the impact of this vulnerability primarily concerns system availability and stability. Linux is widely used across Europe in servers, cloud infrastructure, embedded systems, and critical infrastructure. A deadlock caused by this vulnerability could lead to system freezes or crashes, resulting in downtime and potential disruption of services. This is particularly critical for sectors relying on high availability such as finance, telecommunications, healthcare, and government services. While this vulnerability does not directly expose confidentiality or integrity risks, the denial of service caused by deadlocks can have cascading effects on business operations and incident response capabilities. Systems running real-time or high-reliability workloads are especially vulnerable to the impact of such kernel deadlocks. Since the vulnerability is triggered by NMIs, which are hardware or firmware generated interrupts, the risk is tied to specific hardware and workload conditions, but the potential for unexpected system hangs remains significant.

To mitigate this vulnerability, European organizations should prioritize updating their Linux kernel to the patched versions that include the fix for CVE-2024-48876. Kernel updates should be tested in staging environments to ensure compatibility with existing workloads and hardware. Additionally, organizations should monitor kernel logs and system behavior for signs of deadlock or system hangs related to NMIs. Implementing robust system monitoring and alerting can help detect early symptoms of this issue. For systems where immediate kernel updates are not feasible, consider reducing the frequency or conditions that trigger NMIs if configurable via hardware or firmware settings, although this is a limited workaround. Organizations should also review their incident response and recovery procedures to handle potential system freezes gracefully. Engaging with Linux distribution vendors for timely patches and support is recommended. Finally, documenting and communicating the importance of this update to system administrators and security teams will ensure prompt remediation.