CVE-2024-56648 is a vulnerability identified in the Linux kernel's High-availability Seamless Redundancy (HSR) network subsystem, specifically within the fill_frame_info() function in net/hsr/hsr_forward.c. The issue arises due to insufficient validation of packet length when processing network packets that are crafted to appear as VLAN packets but contain only 14 bytes. The vulnerability is triggered when the kernel's skb->mac_len field, which indicates the MAC header length, is used without adequate boundary checks, leading to potential out-of-bounds memory access. This can cause the kernel to read uninitialized memory, as evidenced by Kernel Memory Sanitizer (KMSAN) reports showing uninitialized value usage in fill_frame_info and hsr_forward_skb functions. The root cause is that fill_frame_info() relies on skb->mac_len but does not extend checks to cover cases where packets are shorter than expected, allowing malformed packets to cause memory safety issues. The vulnerability is exploitable via crafted network packets sent to the affected system, potentially causing kernel crashes or undefined behavior. The vulnerability affects multiple Linux kernel versions as indicated by the affected commit hashes, and it has been publicly disclosed without a CVSS score or known exploits in the wild at the time of publication.

For European organizations, the impact of CVE-2024-56648 can be significant, especially for those relying on Linux-based infrastructure with HSR enabled. HSR is used primarily in industrial and critical network environments requiring high availability and redundancy, such as manufacturing plants, energy grids, transportation systems, and telecommunications. Exploitation could lead to kernel crashes (denial of service), potential memory corruption, or unpredictable system behavior, which in critical environments could disrupt operations or safety systems. Although no known exploits are reported yet, the vulnerability could be leveraged by attackers with network access to send specially crafted packets to vulnerable hosts. This risk is heightened in environments where network segmentation is weak or where Linux systems are exposed to untrusted networks. Confidentiality and integrity impacts are limited as the vulnerability primarily causes memory safety issues rather than direct data leakage or privilege escalation. However, availability impact is medium to high due to potential system instability or crashes. Organizations in Europe with industrial control systems or telecommunications infrastructure running Linux kernels with HSR support should be particularly vigilant.

1. Apply official Linux kernel patches that address CVE-2024-56648 as soon as they become available from trusted sources or Linux distribution vendors. 2. If immediate patching is not possible, disable HSR functionality on Linux systems unless it is strictly required, to reduce the attack surface. 3. Implement strict network segmentation and filtering to limit exposure of vulnerable Linux hosts to untrusted or external networks, especially blocking malformed or suspicious VLAN-tagged packets. 4. Monitor network traffic for anomalous packets that mimic VLAN frames with abnormal lengths, using advanced intrusion detection systems capable of deep packet inspection. 5. Employ kernel runtime security tools that can detect and prevent exploitation attempts involving malformed packets or kernel memory corruption. 6. Maintain up-to-date backups and incident response plans to quickly recover from potential denial-of-service conditions caused by exploitation. 7. Engage with Linux distribution security advisories and subscribe to vulnerability notifications to stay informed about patch releases and exploit developments.