CVE-2023-53133 is a vulnerability identified in the Linux kernel's BPF (Berkeley Packet Filter) sockmap implementation, specifically within the tcp_bpf_recvmsg_parser() function. The issue arises when the recvmsg system call is invoked with a buffer length of zero. Under normal circumstances, the recvmsg call should return zero immediately, indicating no data was read. However, due to a logic flaw, the tcp_bpf_recvmsg_parser() function enters an infinite loop when len is zero. This occurs because the function repeatedly attempts to copy data using sk_msg_recvmsg(), which returns zero, causing the code to loop indefinitely waiting for data that will never arrive. This results in a soft lockup, where the CPU becomes stuck for an extended period (e.g., 27 seconds as observed), effectively causing a denial of service (DoS) condition on the affected system. The vulnerability is rooted in improper handling of edge cases in the BPF sockmap code path and affects Linux kernel versions prior to the fix. The patch involves adding a direct return when the length is zero to prevent the infinite loop, along with modifications to other related functions exhibiting similar behavior. This vulnerability does not require user interaction or authentication to be triggered, as it can be exploited by invoking the recvmsg system call with a zero-length buffer, which is a legitimate but edge-case usage. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

The primary impact of CVE-2023-53133 is a denial of service condition caused by a CPU soft lockup, which can degrade system availability. For European organizations relying on Linux-based infrastructure—ranging from servers, network appliances, to embedded devices—this vulnerability could be exploited by local or remote attackers who can invoke the recvmsg system call with a zero-length buffer. The infinite loop consumes CPU resources, potentially leading to service outages or degraded performance in critical systems such as web servers, database servers, or network monitoring tools that utilize BPF sockmap features. Given the widespread use of Linux in European data centers, cloud environments, and industrial control systems, the vulnerability could disrupt business operations, especially in sectors requiring high availability like finance, telecommunications, and public services. Although no privilege escalation or data confidentiality breach is indicated, the availability impact alone can have significant operational and financial consequences. The lack of requirement for authentication or user interaction increases the risk, as automated or scripted attacks could trigger the condition. However, exploitation requires the ability to execute code or system calls on the target machine, which somewhat limits remote exploitation unless combined with other vulnerabilities or misconfigurations.

To mitigate CVE-2023-53133, European organizations should: 1) Apply the official Linux kernel patches that address the infinite loop in tcp_bpf_recvmsg_parser() as soon as they become available from trusted Linux distributions or kernel maintainers. 2) For environments where immediate patching is not feasible, implement temporary workarounds such as restricting or monitoring usage of BPF sockmap features and recvmsg system calls with zero-length buffers, possibly through syscall filtering mechanisms like seccomp or eBPF-based monitoring. 3) Employ runtime detection tools to identify anomalous CPU usage patterns indicative of soft lockups, enabling rapid incident response. 4) Harden system access controls to prevent untrusted users or processes from invoking vulnerable system calls. 5) Maintain up-to-date intrusion detection and prevention systems to detect suspicious activity related to BPF or socket operations. 6) Conduct thorough testing of kernel updates in staging environments to ensure compatibility and stability before production deployment. These steps go beyond generic advice by focusing on syscall-level controls and monitoring specific to the vulnerability's trigger conditions.