CVE-2024-39487 is a vulnerability identified in the Linux kernel's bonding driver, specifically within the function bond_option_arp_ip_targets_set(). This function is responsible for handling ARP IP target options in network bonding configurations. The vulnerability arises due to an out-of-bounds read when the input string (newval->string) is empty. In such cases, the code attempts to read the byte immediately following the string (newval->string+1), which is outside the allocated memory boundary. This leads to a kernel memory read beyond the intended buffer, triggering a Kernel Address Sanitizer (KASAN) slab-out-of-bounds error. The issue manifests as a read of size 1 at an invalid memory address, causing instability or potential kernel crashes. The root cause is the lack of a proper check on the string length before its usage in strlen and related string operations. The vulnerability was detected in Linux kernel version 6.7.0-rc7 and is reproducible in environments such as QEMU virtual machines. The fix involves adding a validation step to ensure the string is not empty before processing, thereby preventing the out-of-bounds read. While no known exploits are reported in the wild, the vulnerability affects the core Linux kernel networking subsystem, which is widely used across many Linux distributions and environments.

For European organizations, this vulnerability poses a risk primarily to systems running Linux kernels with the affected bonding driver versions. Network bonding is commonly used in enterprise environments to aggregate multiple network interfaces for redundancy and increased throughput. An out-of-bounds read in kernel space can lead to system instability, kernel panics, or crashes, potentially causing denial of service (DoS) conditions. Although this vulnerability does not directly indicate privilege escalation or remote code execution, the resulting kernel instability can disrupt critical network services, impacting availability. Organizations relying on Linux-based servers, network appliances, or virtualized environments that utilize bonding for network resilience could experience outages or degraded performance. Additionally, the vulnerability could be leveraged as part of a multi-stage attack chain if combined with other exploits, increasing the risk to confidentiality and integrity indirectly. The lack of known exploits reduces immediate threat but does not eliminate the risk, especially in high-security environments where kernel stability is paramount.

European organizations should promptly update their Linux kernels to versions where this vulnerability is patched. Since the fix involves adding a string length check in the bonding driver, applying the latest stable kernel releases or vendor-provided security patches is essential. For environments where immediate patching is not feasible, administrators should consider disabling the bonding driver or avoiding the use of ARP IP target options in bonding configurations as a temporary workaround. Monitoring kernel logs for KASAN slab-out-of-bounds errors can help detect attempts to trigger this vulnerability. Network segmentation and limiting access to systems with bonding configurations reduce exposure. Additionally, organizations should implement rigorous testing of kernel updates in staging environments to ensure stability before deployment. Maintaining up-to-date intrusion detection systems (IDS) and endpoint detection and response (EDR) solutions can aid in identifying anomalous behavior related to kernel faults. Finally, documenting and auditing network bonding configurations will help identify systems at risk and prioritize patching efforts.