CVE-2024-57986 is a vulnerability identified in the Linux kernel's Human Interface Device (HID) core subsystem. The issue relates to the handling of Resolution Multipliers within HID reports. Specifically, the function hid_apply_multiplier() incorrectly assumes that every Resolution Multiplier control is contained within a Logical Collection. According to the HID Usage Table specification, a Resolution Multiplier control may be associated with all controls in a report if no Logical Collection is defined. However, the vulnerable code does not account for the scenario where none of the collections found are Logical Collections, leading to a potential null pointer dereference or incorrect behavior. The vulnerability stems from a logical flaw where the multiplier_collection pointer is never set to NULL if a Logical Collection is not found, contrary to the documented behavior. This could result in improper processing of HID reports, potentially causing kernel crashes or undefined behavior. The vulnerability was initially reported by the syzbot fuzzer in 2019, with one related error fixed previously, but this particular flaw remained unpatched until now. The fix involves explicitly setting the multiplier_collection pointer to NULL when the collection found is not a Logical Collection, aligning the implementation with the HID specification. The affected versions are identified by specific Linux kernel commit hashes, indicating the vulnerability is present in certain kernel builds prior to the patch. There are no known exploits in the wild at the time of publication, and no CVSS score has been assigned yet.

For European organizations, this vulnerability poses a risk primarily to systems running affected Linux kernel versions that handle HID devices, such as keyboards, mice, and other human interface peripherals. Exploitation could lead to kernel instability or crashes, resulting in denial of service (DoS) conditions. While the vulnerability does not directly indicate privilege escalation or remote code execution, kernel crashes can disrupt critical services, especially in environments relying on Linux for servers, workstations, or embedded systems. Organizations in sectors such as finance, healthcare, manufacturing, and critical infrastructure that depend on Linux-based systems could experience operational disruptions. Additionally, if attackers develop exploits leveraging this flaw, it could be used as part of a multi-stage attack to compromise system integrity. The impact is heightened in environments where HID devices are frequently used or where kernel stability is paramount. Given the lack of known exploits, the immediate risk is moderate, but the potential for future exploitation necessitates proactive mitigation.

European organizations should prioritize updating their Linux kernels to versions that include the patch for CVE-2024-57986 as soon as it becomes available. Since the vulnerability relates to kernel-level HID handling, kernel updates from trusted Linux distributions should be applied promptly. For environments where immediate patching is not feasible, organizations can consider the following mitigations: 1) Limit the use of untrusted or unknown HID devices, as maliciously crafted HID reports could trigger the vulnerability. 2) Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and Kernel Page Table Isolation (KPTI) to reduce the impact of potential kernel exploits. 3) Monitor system logs for unusual HID-related errors or kernel crashes that may indicate exploitation attempts. 4) Use security modules like SELinux or AppArmor to restrict access to HID device interfaces where possible. 5) In virtualized environments, isolate HID device passthrough to trusted virtual machines only. These targeted mitigations complement patching and reduce the attack surface related to HID device handling.