CVE-2024-56616 is a vulnerability in the Linux kernel's Direct Rendering Manager (DRM) subsystem, specifically within the DisplayPort Multi-Stream Transport (MST) sideband message handling code. The flaw arises from an improper validation of the MST sideband message body length. The message body length must be at least one byte to account for the message body CRC (cyclic redundancy check) at the end of the message. However, some MST branch devices may return a header with a correct header CRC but an incorrectly set body length of zero. This discrepancy leads to a memory corruption issue in the drm_dp_sideband_append_payload() function. The vulnerability manifests as an out-of-bounds array access and an invalid memcpy operation, potentially causing kernel memory corruption. The kernel logs show errors such as UBSAN array-index-out-of-bounds and memcpy field-spanning writes, indicating serious memory safety violations. This flaw could be triggered when the kernel processes MST sideband messages from connected DisplayPort devices, particularly MST branch devices that incorrectly report message lengths. The vulnerability affects Linux kernel versions prior to the patch that fixed the length check, and it is present in the drm_display_helper driver code responsible for DisplayPort MST topology management. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability is technical and low-level, involving kernel memory handling in the graphics subsystem.

For European organizations, the impact of CVE-2024-56616 depends largely on their use of Linux systems with DisplayPort MST-enabled hardware, such as multi-monitor setups in workstations, servers, or embedded devices. Exploitation could lead to kernel memory corruption, potentially causing system crashes (denial of service) or enabling privilege escalation if an attacker can craft malicious MST sideband messages. This could compromise system availability and integrity. Organizations in sectors relying heavily on Linux-based infrastructure with graphical output—such as media production, software development, and certain industrial control systems—may be more affected. The vulnerability could also impact cloud providers and data centers using Linux hosts with DisplayPort MST hardware for remote management or visualization. Although no exploits are known yet, the kernel-level nature of the flaw means that successful exploitation could have severe consequences, including full system compromise. European organizations must consider the risk to critical infrastructure and services that depend on stable Linux kernel operation with graphics hardware.

To mitigate this vulnerability, European organizations should prioritize updating their Linux kernels to versions where the drm_dp_mst sideband message length check has been corrected. Kernel updates from trusted Linux distributions should be applied promptly. For environments where immediate patching is not feasible, organizations can consider disabling MST functionality if not required, thereby reducing the attack surface. Monitoring kernel logs for the specific error messages related to drm_dp_sideband_append_payload and drm_dp_mst_hpd_irq_handle_event can help detect attempts to exploit this flaw. Additionally, organizations should ensure that only trusted DisplayPort MST devices are connected to critical systems to prevent malicious devices from triggering the vulnerability. Employing kernel hardening techniques and enabling security modules like SELinux or AppArmor may help contain potential exploitation impacts. Finally, maintaining a robust incident response plan for kernel-level compromises is advisable.