CVE-2024-49856 is a vulnerability identified in the Linux kernel specifically affecting the Intel Software Guard Extensions (SGX) implementation on x86 architectures. The issue arises in the NUMA (Non-Uniform Memory Access) node search logic for SGX Enclave Page Cache (EPC) memory allocation. When the current NUMA node lacks an EPC section configured by the system firmware, and all EPC sections on other nodes are fully utilized, the CPU can enter an indefinite loop while searching for available EPC pages on remote nodes. This occurs because the variable representing the current node ID (nid_of_current) is not included in the mask of nodes with SGX memory (sgx_numa_mask), causing the loop condition to never be satisfied and resulting in a soft lockup or deadlock. This deadlock effectively halts CPU progress on affected threads, causing system instability or unresponsiveness. The vulnerability does not stem from firmware misconfiguration, as it is valid for firmware to omit EPC sections on some nodes for performance reasons. The fix involves reworking the loop to iterate only over nodes that actually have SGX memory, preventing the deadlock scenario. This vulnerability impacts Linux kernel versions identified by the commit hash 901ddbb9ecf5425183ea0c09d10c2fd7868dce54 and potentially others in the same lineage. No known exploits are reported in the wild as of the publication date. The vulnerability affects systems using Intel SGX technology on Linux, which is commonly used for secure enclave execution to protect sensitive code and data from disclosure or tampering even on compromised systems.

For European organizations, this vulnerability could lead to system instability or denial of service conditions on Linux servers or workstations utilizing Intel SGX technology, particularly in environments with NUMA architectures and firmware configurations that do not provision EPC memory on all nodes. This could affect cloud service providers, financial institutions, research centers, and enterprises relying on SGX for secure computation or data protection. The soft lockup can degrade availability of critical services or applications running within SGX enclaves, potentially disrupting business operations or delaying sensitive computations. While the vulnerability does not directly expose confidential data or allow privilege escalation, the resulting system hangs could cause operational outages or require system reboots, impacting service continuity. Since SGX is often used in security-sensitive contexts, any disruption could undermine trust in secure computing environments. However, the lack of known exploits and the requirement for specific hardware and firmware configurations limit the immediate risk. Organizations using Linux kernels with affected versions and Intel SGX-enabled hardware should consider this vulnerability seriously to maintain system reliability and secure enclave availability.

To mitigate CVE-2024-49856, European organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from trusted sources or Linux distribution vendors. 2) Review firmware configurations to ensure EPC memory sections are provisioned on NUMA nodes where SGX is expected to be used, if feasible, to reduce the risk of encountering the deadlock condition. 3) Monitor system logs and kernel messages for signs of soft lockups or CPU stalls related to SGX memory allocation failures. 4) In environments where SGX is not critical, consider disabling SGX support in BIOS/firmware or kernel configuration to avoid exposure. 5) Test updated kernels in staging environments to confirm the fix resolves the deadlock without introducing regressions. 6) Maintain robust incident response procedures to quickly recover from potential system hangs, including automated reboots or failover mechanisms. 7) Engage with hardware and firmware vendors to ensure compatibility and support for proper EPC memory provisioning on NUMA nodes. These steps go beyond generic advice by focusing on firmware configuration validation, proactive monitoring, and operational readiness to handle potential lockups.