CVE-2021-47202 is a vulnerability identified in the Linux kernel's thermal management subsystem, specifically within the of_thermal_ functions that handle device tree thermal zones and sensors. The vulnerability arises due to improper handling of NULL pointers when the thermal zone device attempts to access a thermal sensor device that has not yet been probed or initialized. The function of_parse_thermal_zones() is responsible for parsing thermal zones and registering thermal_zone devices for each subnode. However, if a thermal zone depends on a thermal sensor device that is not yet available, attempts to set trip point temperatures (trip_point_*_temp) for that thermal zone can lead to a NULL pointer dereference. This results in a kernel crash (kernel panic) due to an invalid memory access, as demonstrated by the kernel call trace provided. The issue affects multiple functions including of_thermal_set_trip_temp(), of_thermal_get_temp(), of_thermal_set_emul_temp(), and of_thermal_get_trend(), all of which were susceptible to NULL pointer dereferences. The vulnerability was addressed by fixing these functions to properly check for NULL pointers before dereferencing them, preventing kernel crashes. The affected Linux kernel versions include those identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and similar versions prior to the patch. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. This vulnerability primarily impacts system stability and availability rather than confidentiality or integrity, as it leads to denial of service through kernel crashes when exploited.

For European organizations, this vulnerability poses a risk primarily to the availability and reliability of Linux-based systems, especially those relying on thermal management via device tree configurations. Systems affected include servers, embedded devices, and IoT devices running vulnerable Linux kernel versions. A successful exploitation could cause system crashes, resulting in downtime, disruption of critical services, and potential data loss due to abrupt shutdowns. Organizations operating data centers, industrial control systems, or critical infrastructure that utilize Linux kernels with affected thermal management code could experience operational interruptions. While the vulnerability does not directly expose sensitive data or allow privilege escalation, the denial of service impact can affect business continuity and service-level agreements. Given the widespread use of Linux in European enterprises, particularly in cloud infrastructure, telecommunications, and manufacturing sectors, the impact could be significant if unpatched systems are exposed to malicious or accidental triggering of this flaw.

European organizations should implement the following specific mitigation steps: 1) Identify and inventory all Linux systems running kernel versions that include the vulnerable commit or earlier. 2) Apply the official Linux kernel patches that fix the NULL pointer dereference in the of_thermal_ functions as soon as they become available from trusted Linux distributions or upstream sources. 3) For embedded or IoT devices where kernel updates are challenging, consider disabling or restricting access to sysfs interfaces that allow writing to trip_point_*_temp attributes to prevent unauthorized or accidental triggering of the vulnerability. 4) Implement monitoring and alerting for kernel panics or thermal subsystem errors to detect potential exploitation attempts or system instability early. 5) Test kernel updates in staging environments to ensure compatibility with existing thermal management configurations before deployment. 6) Engage with hardware and device vendors to confirm that firmware and device tree configurations are compatible with patched kernels to avoid regressions. 7) Limit user privileges to prevent unprivileged users from writing to thermal sysfs attributes, reducing the risk of exploitation via local user interaction.