CVE-2023-52767 is a vulnerability identified in the Linux kernel's TLS (Transport Layer Security) implementation, specifically within the function tls_sw_splice_eof(). The issue arises when this function is executed as part of the sendfile() system call while handling empty plaintext or ciphertext socket message buffers (sk_msg). The vulnerability is triggered because the empty ciphertext buffer lacks sufficient space to accommodate the encryption overhead, causing the tls_push_record() function to incorrectly follow a code path (split = true) intended only for interactions with attached BPF (Berkeley Packet Filter) programs. This leads to confusion in the code flow, ultimately causing tls_merge_open_record() to assume the presence of at least one populated buffer element. Since this assumption is invalid in the case of empty buffers, a NULL pointer dereference occurs, potentially leading to a kernel crash (denial of service). The root cause is a missing check in tls_sw_splice_eof() for empty buffers, which is already handled correctly in tls_sw_push_pending_record(). This vulnerability was discovered by syzkaller, a kernel fuzzing tool, and affects specific Linux kernel commits referenced by their hashes. There are no known exploits in the wild at the time of publication, and no CVSS score has been assigned yet. The vulnerability primarily impacts the Linux kernel's TLS send path, which is critical for secure network communications, especially in environments relying on kernel TLS offloading or accelerated TLS processing.

For European organizations, this vulnerability could have significant operational impacts, particularly for those running Linux-based servers handling encrypted network traffic, such as web servers, mail servers, or VPN gateways. A successful exploitation could cause kernel crashes leading to denial of service conditions, disrupting business-critical services and potentially causing downtime. Although the vulnerability does not directly expose confidential data or allow privilege escalation, the availability impact could be severe in environments with high TLS traffic volumes. Organizations relying on kernel TLS acceleration for performance gains may be more exposed. Additionally, sectors with stringent uptime requirements, such as financial services, healthcare, and critical infrastructure, could face operational and reputational risks if affected systems become unstable. The lack of known exploits reduces immediate risk, but the presence of a kernel NULL dereference vulnerability in a widely deployed OS kernel component warrants prompt attention.

European organizations should prioritize updating their Linux kernel to versions that include the patch for CVE-2023-52767 as soon as vendor patches become available. In the interim, system administrators should audit their use of the sendfile() system call in conjunction with TLS offloading features and consider disabling kernel TLS acceleration if feasible to reduce exposure. Monitoring kernel logs for crashes or anomalies related to TLS operations can help detect attempted exploitation or instability. Additionally, organizations should implement robust kernel crash recovery mechanisms and maintain up-to-date backups to minimize downtime impact. For environments using custom or older kernel versions, backporting the patch or applying vendor-provided fixes is critical. Network segmentation and limiting exposure of vulnerable systems to untrusted networks can further reduce risk. Finally, maintaining awareness through security advisories and coordinating with Linux distribution maintainers will ensure timely patch deployment.