CVE-2021-47650 is a vulnerability identified in the Linux kernel's ALSA System on Chip (ASoC) subsystem, specifically within the soc-compress component responsible for compressed audio handling. The flaw arises due to insufficient validation of a pointer named 'codec_dai' during the registration of sound cards via the snd_soc_register_card() function. The call trace involves multiple functions: snd_soc_register_card() calls snd_soc_bind_card(), which calls soc_init_pcm_runtime(), then snd_soc_dai_compress_new(), and finally snd_soc_new_compress(). The vulnerability occurs when the number of codecs (card->dai_link->num_codecs) is zero, leading to an out-of-bounds index access in asoc_rtd_to_codec(rtd, 0). This results in 'codec_dai' being a null pointer. Without proper null checks, subsequent operations in snd_soc_new_compress() may dereference this null pointer, potentially causing a kernel crash or undefined behavior. The patch involves adding a null check for 'codec_dai' to prevent the function from proceeding if the pointer is null, thereby avoiding use-after-null pointer dereference. The vulnerability affects various Linux kernel versions identified by specific commit hashes. No known exploits are reported in the wild, and no CVSS score has been assigned yet. The issue is rooted in kernel-level audio driver code, which is invoked by multiple platforms, indicating a broad potential attack surface within Linux-based systems that utilize the ASoC framework for audio compression.

For European organizations, the impact of CVE-2021-47650 primarily concerns systems running Linux kernels with the vulnerable ASoC soc-compress component, especially those handling compressed audio streams. Exploitation could lead to kernel crashes (denial of service) or potentially enable privilege escalation if attackers can leverage the null pointer dereference to execute arbitrary code, although no such exploits are currently known. Critical infrastructure, telecommunications, media companies, and any enterprise relying on Linux-based embedded systems or servers with audio processing capabilities may be affected. Disruptions could impact service availability and system stability, leading to operational downtime and potential data integrity issues. Given the Linux kernel's widespread use across servers, desktops, and embedded devices in Europe, the vulnerability poses a moderate risk, particularly in environments where audio compression features are actively used or where attackers have local access to the system. However, remote exploitation likelihood appears low due to the nature of the vulnerability requiring specific kernel subsystem interaction.

European organizations should prioritize updating their Linux kernel to versions where this vulnerability is patched. Since the issue stems from kernel code, applying official Linux kernel updates or vendor-provided patches that include the fix is the most effective mitigation. For embedded systems or distributions with slower update cycles, consider disabling or restricting the use of the ASoC soc-compress functionality if audio compression is not required. Additionally, implement strict access controls to limit unprivileged user access to audio device interfaces, reducing the risk of exploitation. Monitoring kernel logs for unusual snd_soc subsystem errors may help detect attempted exploitation. Organizations should also maintain robust system integrity verification and employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and Control Flow Integrity (CFI) to mitigate potential exploitation paths. Finally, coordinate with Linux distribution vendors to ensure timely patch deployment and verify that all affected systems receive updates promptly.