CVE-2024-46783 is a vulnerability identified in the Linux kernel's TCP BPF (Berkeley Packet Filter) subsystem, specifically within the tcp_bpf_sendmsg() function. The issue arises when messages are corked in the psock->cork buffer, and the final message triggers a flush operation that attempts to send a sk_msg larger than the current message size. This causes the variable 'copied' to become negative in the tcp_bpf_send_verdict() function, particularly at the code line where '*copied -= (tosend + delta);' is executed. Using a negative 'copied' value as a return value leads to a kernel BUG, causing an internal kernel error and a system crash (kernel panic). The vulnerability was discovered through syzbot fuzzing and results in a BUG at net/socket.c, which manifests as a kernel oops and crash. The stack trace shows the failure occurs during the socket sendmsg syscall path, affecting ARM64 architecture among others. This bug can be triggered by sending crafted TCP messages that exploit the corking and flushing logic in the tcp_bpf_sendmsg() function. The root cause is improper handling of message sizes and return values in the TCP BPF sendmsg path, leading to negative counters and kernel instability. No known exploits are reported in the wild yet, and no CVSS score has been assigned. The vulnerability affects Linux kernel versions identified by the commit hash 4f738adba30a7cfc006f605707e7aee847ffefa0 and possibly others in the same branch. This flaw can cause denial of service by crashing the kernel when exploited.

For European organizations, this vulnerability poses a significant risk primarily in environments running vulnerable Linux kernel versions, especially on servers, network appliances, and embedded devices using TCP BPF features. The impact is mainly a denial of service (DoS) condition caused by kernel crashes, which can disrupt critical services, including web servers, database servers, and network infrastructure components. Organizations relying on Linux-based systems for critical infrastructure, cloud services, or telecommunications may experience outages or degraded service availability. Although no privilege escalation or remote code execution is indicated, the ability to cause kernel panics remotely or locally can be leveraged by attackers to disrupt operations or as part of a larger attack chain. The vulnerability could affect cloud providers, hosting services, and enterprises with Linux-based network stacks, impacting business continuity and potentially causing financial and reputational damage. Given the widespread use of Linux in European IT environments, the risk of service disruption is non-trivial, especially in sectors like finance, healthcare, and government where uptime is critical.

To mitigate this vulnerability, European organizations should: 1) Apply the official Linux kernel patches that fix the tcp_bpf_sendmsg() return value handling as soon as they are released and validated. 2) Monitor Linux kernel updates from trusted sources and prioritize patching in production environments using affected kernel versions. 3) Implement kernel live patching solutions where possible to reduce downtime during patch deployment. 4) Restrict access to systems running vulnerable kernels, especially limiting untrusted user or network access that could trigger the vulnerability. 5) Use network segmentation and firewall rules to limit exposure of vulnerable services. 6) Employ kernel crash monitoring and alerting to detect and respond quickly to any exploitation attempts. 7) For critical infrastructure, consider deploying intrusion detection systems capable of identifying abnormal TCP BPF activity or malformed TCP messages that could trigger the bug. 8) Validate and test patches in staging environments to ensure stability before production rollout. 9) Maintain robust backup and recovery procedures to minimize impact in case of service disruption.