CVE-2023-52986 is a vulnerability in the Linux kernel related to the handling of socket protocols (sk_prot) when using BPF (Berkeley Packet Filter) sockmaps. Sockmaps allow attaching BPF programs to sockets for advanced packet processing. The issue arises when a listening TCP socket linked to a sockmap has its sk_prot overridden to point to one of several variants in the tcp_bpf_prots structure, depending on the socket family and attached BPF programs. When a child socket is cloned from such a listener, it initially inherits the parent's sk_prot. The kernel code attempts to restore the child's sk_prot to the original non-BPF variant during cloning via the tcp_bpf_clone function. However, the existing check only verifies if the sk_prot matches the TCP_BPF_BASE variant, ignoring other tcp_bpf_prots variants. If the listener's sk_prot is any other variant, the child socket retains the inherited sk_prot incorrectly. This improper inheritance can cause severe issues such as infinite recursion during socket close operations because the child's state is not properly configured for tcp_bpf_prot operations. The vulnerability stems from an incomplete check in tcp_bpf_clone and the complex state transitions sockets can undergo while linked to sockmaps, including transitioning to TCP_LISTEN state after being inserted into a sockmap. The fix involves adjusting the check to detect all tcp_bpf_prots variants to ensure correct sk_prot restoration. No known exploits are reported in the wild, and no CVSS score has been assigned yet.

For European organizations, this vulnerability poses a risk primarily to systems running Linux kernels with BPF sockmap support enabled and actively used, especially in environments leveraging advanced networking features such as container orchestration, network function virtualization, or custom packet filtering. The infinite recursion on socket close can lead to kernel crashes or denial of service (DoS), impacting availability of critical network services. This can disrupt business operations, especially for service providers, cloud infrastructure operators, and enterprises relying on Linux-based network appliances. Although exploitation requires specific conditions (use of sockmaps with TCP listeners), the complexity and subtlety of the bug could lead to unexpected system instability or crashes, complicating incident response. Confidentiality and integrity impacts are less direct but could arise if attackers leverage DoS conditions to facilitate further attacks or evade detection. The lack of known exploits suggests limited immediate threat, but the vulnerability's presence in widely deployed Linux kernels means European organizations should prioritize patching to maintain network reliability and security.

1. Apply the official Linux kernel patches that address CVE-2023-52986 as soon as they become available from trusted sources or Linux distributions. 2. Audit and monitor the use of BPF sockmaps in your environment; disable or restrict their use if not required, reducing the attack surface. 3. Implement kernel live patching solutions where possible to minimize downtime during patch deployment. 4. Enhance monitoring for kernel crashes or unusual socket behavior that might indicate exploitation attempts or instability related to this vulnerability. 5. For organizations using container orchestration platforms (e.g., Kubernetes) or network virtualization, verify that underlying host kernels are patched and that network plugins do not expose vulnerable configurations. 6. Engage in proactive vulnerability management to track Linux kernel updates and security advisories related to BPF and networking subsystems. 7. Consider isolating critical network functions on dedicated hosts with hardened kernel configurations to limit impact scope.