CVE-2024-26885 is a vulnerability identified in the Linux kernel's BPF (Berkeley Packet Filter) subsystem, specifically within the DEVMAP_HASH map type implementation on 32-bit architectures. The issue arises from an integer overflow during the calculation of the number of hash buckets allocated for the map. The devmap code attempts to allocate a number of hash buckets equal to the next power of two of the max_entries parameter. However, on 32-bit systems, the calculation involves a left-shift operation by 32 bits on an unsigned long value, which is undefined behavior because unsigned long is 4 bytes on these architectures. This can cause the value to overflow mid-calculation, leading to an incorrect bucket count. The existing overflow check is performed after rounding up to the next power of two and checks if the truncated 32-bit value is zero, which is insufficient due to the undefined behavior of the shift operation. This flaw can be triggered by creating a DEVMAP_HASH with max_entries greater than 0x80000000 and attempting to update it, causing a kernel crash (denial of service) on affected systems, as demonstrated on arm32 by Syzbot. The fix involves moving the overflow check to before the rounding operation to prevent the undefined behavior and ensure safe allocation sizes. No known exploits are currently reported in the wild, and the vulnerability affects Linux kernel versions prior to the patch commit identified by the hash 6f9d451ab1a33728adb72d7ff66a7b374d665176. This vulnerability is specific to 32-bit architectures, which are less common but still in use in embedded and specialized systems.

For European organizations, the primary impact of CVE-2024-26885 is the potential for denial of service (DoS) on Linux systems running on 32-bit architectures, particularly those using the BPF DEVMAP_HASH feature. While many enterprise and server environments have largely transitioned to 64-bit systems, embedded devices, IoT infrastructure, and certain industrial control systems in sectors such as manufacturing, telecommunications, and critical infrastructure may still rely on 32-bit Linux kernels. A successful exploitation could cause kernel crashes, leading to system downtime, disruption of services, and potential operational impacts. Although no privilege escalation or remote code execution is indicated, the DoS could be leveraged as part of a broader attack chain or to disrupt critical services. European organizations with legacy or embedded Linux devices should be aware of this risk, especially in environments where uptime and reliability are critical. The lack of known exploits reduces immediate risk, but the vulnerability's presence in the kernel source means attackers could develop exploits if motivated. Additionally, the vulnerability highlights the importance of patching and kernel updates in embedded and specialized Linux deployments.

To mitigate CVE-2024-26885, European organizations should: 1) Identify and inventory Linux systems running on 32-bit architectures, focusing on those using BPF features or DEVMAP_HASH maps. 2) Apply the official Linux kernel patches that fix this vulnerability, specifically the commit identified by hash 6f9d451ab1a33728adb72d7ff66a7b374d665176 or later stable kernel releases that include this fix. 3) For embedded or IoT devices where kernel updates are challenging, consider vendor firmware updates or consult with device manufacturers for patched versions. 4) Implement monitoring for unusual kernel crashes or system instability that could indicate attempts to exploit this vulnerability. 5) Restrict untrusted users from creating or manipulating BPF maps, especially DEVMAP_HASH types, by enforcing strict access controls and capabilities (e.g., limiting CAP_BPF or CAP_SYS_ADMIN privileges). 6) Conduct security reviews of custom or third-party kernel modules that interact with BPF to ensure they do not expose similar risks. 7) Maintain a robust patch management process for embedded and specialized Linux devices, which are often overlooked compared to standard servers and desktops.