CVE-2024-56764 is a high-severity use-after-free vulnerability in the Linux kernel's ublk (user block) driver subsystem. The vulnerability arises from improper handling of the gendisk structure during the addition of a disk device. Specifically, when the add_disk() function fails, the gendisk pointer may have already been freed, but the ublk_abort_requests() function still attempts to access it to abort all inflight requests. This results in a use-after-free condition (CWE-416), which can lead to memory corruption. The vulnerability occurs because ublk_abort_requests() is called either when exiting the io_uring context or when handling a timeout, and it assumes the gendisk reference is valid. The fix involves detaching the gendisk from the ublk device if add_disk() fails, preventing the use-after-free scenario. The vulnerability has a CVSS 3.1 score of 7.8, indicating high severity, with attack vector local (AV:L), low attack complexity (AC:L), requiring low privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). No known exploits are currently reported in the wild. This vulnerability affects Linux kernel versions identified by the commit hash bd23f6c2c2d00518e2f27f2d25cef795de9bee56 and likely related versions around that commit. Because the Linux kernel is widely used in servers, desktops, and embedded devices, this vulnerability could be exploited by local attackers with some privileges to cause system crashes, escalate privileges, or execute arbitrary code, potentially compromising system confidentiality, integrity, and availability.

For European organizations, this vulnerability poses a significant risk, especially for those relying on Linux-based infrastructure such as servers, cloud environments, and embedded systems. Exploitation could allow attackers with local access to crash critical systems or execute arbitrary code with elevated privileges, leading to data breaches, service disruptions, or lateral movement within networks. Sectors such as finance, healthcare, telecommunications, and government agencies, which often use Linux servers for critical workloads, could face operational downtime and data integrity issues. The high impact on confidentiality, integrity, and availability means sensitive data could be exposed or manipulated, and critical services could be interrupted. Additionally, the vulnerability's presence in the io_uring subsystem, which is increasingly used for high-performance asynchronous I/O operations, means that high-throughput systems could be particularly vulnerable to exploitation attempts causing denial of service or privilege escalation.

European organizations should promptly apply the official Linux kernel patches that address CVE-2024-56764 once available. Until patches are deployed, organizations should limit local access to systems running vulnerable Linux kernel versions by enforcing strict access controls and monitoring for suspicious local activity. Employ kernel-level security modules such as SELinux or AppArmor to restrict the capabilities of processes interacting with the ublk subsystem. Regularly audit and update Linux kernel versions to ensure all security fixes are applied timely. For environments using io_uring heavily, consider temporarily disabling or restricting its usage if feasible. Implement comprehensive logging and alerting to detect anomalous behavior related to disk operations or kernel crashes. Additionally, conduct vulnerability scanning and penetration testing focused on local privilege escalation vectors to identify potential exploitation attempts. Finally, maintain robust incident response plans to quickly contain and remediate any exploitation.