CVE-2024-35921 is a vulnerability identified in the Linux kernel, specifically within the MediaTek video codec (vcodec) driver component that handles HEVC (High Efficiency Video Coding) decoding. The flaw arises from improper handling of the stateless HEVC decoder's initialization process. When the HEVC decoder initialization fails, the driver erroneously saves a pointer to the decoder instance in the context regardless of success or failure. This leads to a use-after-free condition because the pointer is freed during the deinitialization process if initialization fails, but the stale pointer remains stored and can be accessed later. The vulnerability manifests as an oops (kernel crash) triggered by the function vcodec_vpu_send_msg in the MediaTek vcodec driver, which is part of the Linux kernel's media subsystem. The call trace indicates that the issue occurs during the deinitialization and release of the video codec context, specifically in functions like vpu_dec_deinit and vdec_hevc_slice_deinit. This bug can cause kernel instability or crashes when processing HEVC video streams on affected hardware platforms, such as the Acer Tomato (rev3 - 4) board, which uses the MediaTek video codec hardware. The root cause is a failure to conditionally store the instance pointer only upon successful initialization, which was fixed by ensuring the pointer is saved only if initialization succeeds. There is no CVSS score assigned yet, and no known exploits in the wild have been reported. The vulnerability was published on May 19, 2024, and is relevant to Linux kernel versions containing the affected MediaTek vcodec driver code. This flaw is a typical use-after-free vulnerability that can lead to denial of service through kernel crashes and potentially could be leveraged for privilege escalation or arbitrary code execution if combined with other vulnerabilities, although such exploitation is not confirmed at this time.

For European organizations, the impact of CVE-2024-35921 primarily involves potential system instability and denial of service on Linux systems utilizing MediaTek video codec hardware, particularly those processing HEVC video streams. This could affect servers, embedded devices, or workstations running vulnerable Linux kernels with MediaTek vcodec support enabled. Organizations relying on multimedia processing, video streaming, or embedded Linux devices with MediaTek chipsets may experience unexpected kernel crashes, leading to service interruptions or degraded performance. While no active exploits are known, the vulnerability could be targeted by attackers to disrupt operations or as a stepping stone for privilege escalation in multi-user environments. The impact is more pronounced in sectors with critical multimedia infrastructure, such as broadcasting, media production, telecommunications, and IoT deployments. Additionally, since Linux is widely used in European data centers and embedded systems, unpatched systems could face increased risk of stability issues. The vulnerability does not directly expose data confidentiality or integrity but affects availability and system reliability. Given the kernel-level nature of the flaw, successful exploitation could undermine system security controls, emphasizing the need for timely patching.

European organizations should take the following specific mitigation steps: 1) Identify Linux systems using MediaTek video codec hardware or running kernels with the affected vcodec driver. 2) Apply the latest Linux kernel patches that address CVE-2024-35921 as soon as they become available from trusted sources such as the official Linux kernel repositories or vendor distributions. 3) For embedded or specialized devices (e.g., Acer Tomato boards or similar hardware), coordinate with hardware vendors for firmware or kernel updates incorporating the fix. 4) If immediate patching is not feasible, consider disabling or restricting HEVC video decoding functionality in the MediaTek vcodec driver to prevent triggering the vulnerable code paths. 5) Monitor system logs for kernel oops or crashes related to vcodec operations to detect potential exploitation attempts or instability. 6) Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and Control Flow Integrity (CFI) to reduce exploitation likelihood. 7) Maintain robust incident response and recovery plans to quickly address any service disruptions caused by this vulnerability. These steps go beyond generic advice by focusing on hardware-specific identification, vendor coordination, and operational monitoring tailored to this vulnerability.