CVE-2021-47105 is a vulnerability identified in the Linux kernel's handling of AF_XDP sockets, specifically related to the management of xsk buffers within the kernel's ring buffer mechanism. AF_XDP is a high-performance packet processing interface that allows user-space applications to receive and transmit packets directly, bypassing much of the kernel networking stack. The vulnerability arises because the kernel code responsible for cleaning up the ring buffer entries does not properly return xsk buffers back to the buffer pool after use. Instead, it only nullifies the xdp_buff pointer in the internal software ring but fails to call xsk_buff_free(), which is necessary to release the buffer back to the umem (user memory) pool. This omission causes buffers to be leaked, meaning they are removed from the pool and never reused, leading to a gradual depletion of available buffers. Over time, this can degrade the performance of applications relying on AF_XDP sockets or cause them to fail due to resource exhaustion. The fix involves adding the missing xsk_buff_free() call during the cleanup routine and ensuring that only the actual space left to be cleaned in the ring is processed, rather than the entire ring. This correction prevents buffer leaks and maintains the efficient reuse of memory buffers in the AF_XDP subsystem. The vulnerability does not require user interaction or authentication to be triggered, but it is limited to systems using AF_XDP sockets, which are typically employed in high-performance networking scenarios such as packet processing, network function virtualization, or specialized network appliances running Linux kernels with this feature enabled. No known exploits are reported in the wild as of the publication date.

For European organizations, the impact of CVE-2021-47105 depends largely on their use of Linux systems employing AF_XDP sockets for network packet processing. Organizations operating data centers, telecom infrastructure, or network appliances that leverage Linux kernel features for high-speed packet processing could experience degraded network performance or service interruptions due to buffer exhaustion caused by this vulnerability. This could affect critical services such as telecommunications, cloud service providers, financial trading platforms, and large-scale web services that require low-latency and high-throughput networking. The gradual buffer leak could lead to denial of service conditions or increased latency, impacting service availability and reliability. Confidentiality and integrity impacts are minimal since the vulnerability relates to resource management rather than direct code execution or privilege escalation. However, availability degradation in critical network infrastructure can have significant operational and financial consequences. Since no known exploits exist in the wild, the immediate risk is moderate, but organizations should prioritize patching to prevent potential future exploitation or inadvertent service disruptions.

To mitigate CVE-2021-47105, European organizations should: 1) Identify Linux systems running kernels with AF_XDP socket support, particularly those involved in high-performance networking or packet processing roles. 2) Apply the official Linux kernel patches that include the fix for this vulnerability, ensuring the xsk_buff_free() call is properly integrated in the ring cleanup routines. 3) Monitor system logs and network performance metrics for signs of buffer exhaustion or degraded AF_XDP socket performance, which could indicate unpatched or vulnerable systems. 4) Limit the use of AF_XDP sockets to trusted applications and environments, reducing the attack surface. 5) Implement resource monitoring and alerting specifically for AF_XDP buffer pools to detect abnormal buffer usage patterns early. 6) For environments where immediate patching is not feasible, consider temporarily disabling AF_XDP socket usage or isolating affected systems to minimize impact. 7) Maintain up-to-date inventories of kernel versions and network subsystem configurations to streamline vulnerability management and patch deployment.