CVE-2024-39488 is a vulnerability in the Linux kernel specifically affecting the arm64 architecture related to the handling of bug entries in kernel modules when the CONFIG_DEBUG_BUGVERBOSE kernel configuration option is disabled (set to 'n'). The issue arises from improper alignment and padding of the last bug_entry structure in the bug table used by kernel modules. The arm64 ABI requires natural alignment of struct fields up to 8 bytes, and padding must be added within structs to maintain proper alignment in arrays. When CONFIG_DEBUG_BUGVERBOSE=n, the bug_entry struct is 8 bytes with 6 bytes of data and 2 bytes of trailing padding, requiring 4-byte alignment. However, the assembly code creating bug_entry entries aligns only the start of each entry to 4 bytes but does not align the end. This omission causes the last bug_entry in a module's bug table to lack the necessary trailing padding bytes. While the main kernel image's bug table search (find_bug()) does not depend on trailing padding, the module_bug_finalize() function calculates the number of bug entries by dividing the section size by the size of a bug_entry struct. Due to missing padding, the last entry is not counted, leading module_find_bug() to miss it during bug address lookups. This can cause an unhandled bug condition in kernel modules, resulting in an unexpected kernel panic. The vulnerability can be triggered by loading a kernel module that contains a WARN() macro call, which generates a bug entry. The provided example module triggers a kernel panic upon loading, demonstrating the issue. This vulnerability affects Linux kernel versions containing the specified commit hashes and is specific to arm64 systems with CONFIG_DEBUG_BUGVERBOSE disabled. No known exploits are reported in the wild yet, and no CVSS score has been assigned. The root cause is a subtle assembly-level alignment bug affecting kernel module bug handling, leading to potential system crashes due to unhandled kernel bugs.

For European organizations running Linux on arm64 architectures—commonly found in servers, embedded systems, and increasingly in cloud infrastructure—this vulnerability poses a risk of unexpected kernel panics when loading certain kernel modules that trigger bug entries. Such panics can cause system downtime, disrupt critical services, and potentially lead to data loss or corruption if the kernel crashes during sensitive operations. The impact is particularly significant for environments relying on custom or third-party kernel modules that may use WARN() or similar debugging macros. Industrial control systems, telecommunications infrastructure, and cloud providers using arm64 Linux servers in Europe could experience service interruptions. Although exploitation requires loading a specially crafted kernel module, which typically requires administrative privileges, the vulnerability could be leveraged by attackers with local access or through supply chain compromises injecting malicious modules. The lack of user interaction and the kernel-level nature of the bug mean that once triggered, recovery may require system reboot and manual intervention, impacting availability and operational continuity.

European organizations should promptly update their Linux kernels to versions that include the patch fixing CVE-2024-39488. Since the vulnerability is related to kernel module bug handling on arm64 with CONFIG_DEBUG_BUGVERBOSE disabled, organizations should: 1) Audit kernel configurations to verify if CONFIG_DEBUG_BUGVERBOSE is disabled and consider enabling it if feasible, as it changes the bug_entry layout and avoids the issue. 2) Restrict loading of untrusted or unsigned kernel modules by enforcing strict module signing policies and using kernel lockdown features to prevent unauthorized module insertion. 3) Monitor kernel logs for WARN() and BUG() messages that might indicate triggering of bug entries and potential instability. 4) For critical systems, implement kernel live patching solutions where possible to apply fixes without downtime. 5) Conduct thorough testing of custom kernel modules on patched kernels before deployment. 6) Employ host-based intrusion detection systems to detect anomalous module loading activities. These steps go beyond generic advice by focusing on configuration auditing, module trust enforcement, and proactive monitoring tailored to this vulnerability's characteristics.