CVE-2024-35920 is a vulnerability identified in the Linux kernel specifically affecting the MediaTek video codec (vcodec) driver. The issue arises from the lack of proper locking mechanisms protecting the decoder context list (ctx_list) within the 'vpu_dec_ipi_handler' function. This function handles inter-processor interrupts (IPI) related to the video processing unit (VPU) decoder. Without adequate locking, the ctx_list can be accessed after it has been deleted due to unexpected behavior in the System Control Processor (SCP) IP block, leading to a NULL pointer dereference. This results in a kernel panic and a fatal exception, causing the system to crash and stop secondary CPUs. The vulnerability is hardware-specific, noted on the Google Juniper sku16 board (Device Tree), which uses MediaTek’s MT8183 SoC. The root cause is a race condition where the decoder context list is accessed concurrently without synchronization, leading to use-after-free or NULL pointer dereference scenarios. The kernel panic trace indicates that the issue occurs deep within the MediaTek-specific kernel modules handling video decoding and SCP interrupts. This vulnerability does not have a CVSS score assigned yet and no known exploits in the wild have been reported. However, the impact is a denial of service (DoS) condition due to kernel crashes triggered by malformed or unexpected input to the video codec driver. The patch involves adding a lock to protect the ctx_list, preventing access to freed or NULL pointers and ensuring thread-safe operations within the vpu_dec_ipi_handler function.

For European organizations, this vulnerability primarily poses a risk of denial of service on systems running affected Linux kernels with MediaTek video codec drivers, especially on hardware platforms using MediaTek SoCs like the MT8183. This could impact embedded devices, IoT devices, or specialized hardware using this chipset, potentially disrupting services relying on video decoding capabilities. Although the vulnerability does not directly lead to privilege escalation or remote code execution, the kernel panic and system crash can cause significant availability issues, particularly in environments where uptime is critical such as telecommunications, industrial control systems, or media streaming services. Organizations using Linux-based devices with MediaTek hardware in their infrastructure or products may face operational disruptions or require emergency patching. The lack of known exploits reduces immediate risk, but the vulnerability’s presence in the kernel means that any attacker with local access or the ability to trigger the vulnerable code path could cause system instability. This is especially relevant for European sectors with stringent availability requirements and regulatory compliance mandates around system reliability and incident response.

1. Apply Kernel Updates: European organizations should prioritize updating their Linux kernels to versions that include the patch adding proper locking to the MediaTek vcodec driver. Monitor Linux kernel mailing lists and vendor advisories for the official patch release. 2. Hardware Inventory and Assessment: Identify all devices and systems using MediaTek SoCs, particularly MT8183 or similar, to assess exposure. This includes embedded systems, IoT devices, and specialized hardware running Linux. 3. Restrict Access: Limit local access to affected systems to trusted personnel only, as exploitation requires triggering the vulnerable function locally or via crafted input to the video codec driver. 4. Monitor Logs and System Behavior: Implement monitoring for kernel panics, unexpected reboots, or crashes related to video decoding processes to detect potential exploitation attempts or instability. 5. Vendor Coordination: Engage with hardware vendors and Linux distribution maintainers to ensure timely patch deployment and receive guidance on mitigating this vulnerability in specific device contexts. 6. Consider Workarounds: If immediate patching is not feasible, consider disabling or restricting use of the MediaTek video codec driver on affected devices, if this does not impact critical functionality. 7. Incident Response Preparedness: Prepare for potential denial of service incidents by having recovery procedures and backups in place to minimize downtime.