CVE-2022-49698 is a vulnerability identified in the Linux kernel's netfilter subsystem, specifically related to the use of random number generation functions within kernel code paths. The issue arises from the use of the prandom function, which maintains a per-CPU random state that can be updated from user context, such as the local_out path. This update can cause bottom halves (bh) to occur, leading to potential concurrency issues. The vulnerability is exemplified by a kernel BUG triggered when smp_processor_id() is called in preemptible code, as observed in the nft_ng_random_eval function within the nft_numgen module. The root cause is the unsafe use of prandom in contexts where preemption is enabled, which can lead to race conditions or inconsistent state. The fix involves replacing prandom with get_random_u32, which uses the kernel's random driver and avoids the need for local per-CPU prandom state. This change not only eliminates the concurrency risk but also aligns with prior improvements where prandom was updated to use the real random driver for non-deterministic randomness. The vulnerability does not have reported exploits in the wild and was published in early 2025. It affects Linux kernel versions identified by specific commit hashes, indicating a code-level flaw rather than a configuration or user-space issue. The vulnerability is technical and subtle, involving kernel preemption and random number generation synchronization, which are critical for kernel stability and security.

For European organizations, the impact of CVE-2022-49698 primarily concerns the stability and security of Linux-based systems, especially those utilizing netfilter for packet filtering and firewall functionalities. Since Linux is widely deployed in servers, cloud infrastructure, networking equipment, and embedded devices across Europe, this vulnerability could lead to kernel crashes (denial of service) or unpredictable behavior in network packet processing. While there is no direct evidence of privilege escalation or remote code execution, kernel bugs can be leveraged in complex attack chains or cause service disruptions. Organizations relying on Linux for critical infrastructure, including telecommunications, finance, and government services, may experience operational impacts if vulnerable kernels are exploited or encounter instability. The lack of known exploits reduces immediate risk, but the vulnerability's nature suggests that attackers with kernel-level access or local user privileges could trigger system crashes or instability, potentially impacting availability and reliability of services.

European organizations should prioritize updating their Linux kernel to versions that include the patch replacing prandom with get_random_u32 in the netfilter subsystem. Since the vulnerability involves kernel code, applying official kernel updates from trusted Linux distributions is the most effective mitigation. For environments where immediate patching is challenging, organizations should audit and restrict local user access to systems running vulnerable kernels to reduce the risk of exploitation. Monitoring kernel logs for BUG messages related to smp_processor_id() or nft_ng_random_eval can help detect attempts to trigger the issue. Additionally, organizations should review their use of nftables and netfilter configurations to ensure they follow best practices and minimize exposure. For embedded or specialized devices, coordination with vendors to obtain patched firmware or kernel versions is critical. Finally, integrating this vulnerability into vulnerability management and patching workflows will ensure timely remediation.