CVE-2022-48839 is a vulnerability in the Linux kernel's networking subsystem, specifically within the AF_PACKET socket implementation. The flaw arises in the packet_recvmsg() function, which handles receiving messages on AF_PACKET sockets using PACKET_COPY_THRESH and mmap operations. The issue was discovered by syzbot, an automated kernel fuzzer, which identified a slab-out-of-bounds access caused by tpacket_rcv() queueing socket buffers (skbs) containing uninitialized or garbage data in the skb->cb[] control buffer. This leads to an out-of-bounds memory copy when packet_recvmsg() attempts to copy this data to user space, triggering a stack-out-of-bounds write detected by Kernel Address Sanitizer (KASAN). The root cause is that 12 bytes of metadata in the skb->cb[] buffer are not properly cleared before being copied, which can result in leaking kernel stack data or corrupting memory. The vulnerability affects Linux kernel versions prior to the patch that ensures these bytes are zeroed out before copying. The flaw is triggered when applications use AF_PACKET sockets with PACKET_COPY_THRESH and mmap, a relatively specialized use case often employed in high-performance packet capture or network monitoring tools. The kernel call stack and memory dump indicate the vulnerability manifests during the recvmsg syscall path, with no direct indication of privilege escalation but a potential for information disclosure or memory corruption. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2022-48839 depends on their use of Linux systems running vulnerable kernel versions and employing AF_PACKET sockets with PACKET_COPY_THRESH and mmap. This vulnerability could lead to kernel memory corruption or leakage of sensitive kernel stack data, potentially undermining system confidentiality and stability. Organizations relying on Linux-based network appliances, intrusion detection systems, or custom packet capture solutions may be at higher risk. Exploitation could allow attackers with local user access to cause denial of service via kernel crashes or possibly gain further foothold by corrupting kernel memory. Given the widespread use of Linux in European data centers, cloud infrastructure, and embedded systems, the vulnerability poses a moderate risk, especially in environments where untrusted users have shell access or can run code. However, the specialized nature of the attack vector and lack of remote exploitability limit the threat primarily to local privilege escalation or information disclosure scenarios.

European organizations should prioritize patching Linux kernels to versions that include the fix for CVE-2022-48839, ensuring that the skb->cb[] buffer is properly cleared before copying to user space. Since the vulnerability involves AF_PACKET sockets with PACKET_COPY_THRESH and mmap, organizations should audit their systems for applications or services using these features and restrict or monitor their usage. Employing kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments can help detect similar issues early. Additionally, enforcing strict access controls to limit local user privileges and using containerization or sandboxing to isolate untrusted code can reduce exploitation risk. Network monitoring should be enhanced to detect anomalous use of AF_PACKET sockets or suspicious packet capture activity. Finally, organizations should maintain up-to-date inventories of Linux kernel versions deployed across their infrastructure to ensure timely patch management.