CVE-2021-46996 is a vulnerability identified in the Linux kernel's netfilter nftables subsystem. The issue arises from a memory leak caused by improper handling of userdata allocation failures during the creation of new nftables objects. Specifically, when the allocation of userdata fails, the kernel does not correctly release the associated object name, leading to a memory leak. This flaw is rooted in the error path of the object creation process within nftables, a framework used for packet filtering and network address translation in Linux. Although the vulnerability does not directly enable code execution or privilege escalation, the memory leak can degrade system stability and performance over time, especially on systems with heavy nftables usage. The vulnerability has been addressed by ensuring that the object name is properly released if userdata allocation fails, preventing the memory leak. There are no known exploits in the wild at this time, and no CVSS score has been assigned. The affected versions correspond to specific Linux kernel commits prior to the fix. This vulnerability is primarily a resource management issue within the kernel's networking stack.

For European organizations, the impact of CVE-2021-46996 is primarily related to system reliability and availability rather than direct compromise of confidentiality or integrity. Organizations running Linux servers that utilize nftables for firewalling or network filtering could experience gradual memory consumption increases leading to potential denial of service conditions if the vulnerability is triggered repeatedly. This could affect critical infrastructure, web servers, or network appliances relying on Linux. While exploitation requires triggering the error path in nftables, which may not be trivial, persistent exploitation could degrade service availability. Given the widespread use of Linux in European enterprises, cloud providers, and government agencies, unpatched systems could face operational disruptions. However, the lack of known exploits and the nature of the vulnerability suggest the immediate risk is moderate. Nonetheless, in environments with high network traffic and complex nftables rules, the risk of memory exhaustion and service degradation is more pronounced.

European organizations should promptly apply the Linux kernel patches that address this vulnerability to ensure the memory leak is resolved. Specifically, updating to the latest stable kernel versions that include the fix for CVE-2021-46996 is critical. Organizations should audit their use of nftables to identify systems heavily reliant on this subsystem and prioritize patching those systems. Additionally, monitoring system memory usage and nftables logs can help detect abnormal resource consumption indicative of exploitation attempts. Implementing resource limits and watchdog mechanisms to restart nftables or affected services upon detecting memory leaks can mitigate impact. For environments where immediate patching is challenging, temporarily reducing nftables complexity or traffic load may reduce the risk of triggering the vulnerability. Finally, maintaining robust incident response procedures and keeping abreast of any emerging exploit reports is advisable.