CVE-2025-39728 is a vulnerability identified in the Linux kernel specifically affecting the Samsung clock (clk) driver subsystem. The issue arises from an out-of-bounds array access in the samsung_clk_init() function. The root cause is the dereferencing of the pointer ctx->clk_data.hws before the corresponding ctx->clk_data.num is initialized with the number of clocks (nr_clks). This leads to undefined behavior and triggers a panic under Undefined Behavior Sanitizer (UBSAN) with the UBSAN_ARRAY_BOUNDS error. The panic occurs because the code attempts to access elements of an array that have not been properly allocated or indexed, causing a kernel crash. The call trace indicates that the problem propagates through samsung_clk_init, samsung_cmu_register_one, and exynos_arm64_register_cmu functions, which are part of the clock management infrastructure for Samsung Exynos SoCs (System on Chips). This vulnerability is specific to certain Linux kernel versions identified by the commit hash e620a1e061c4738e26c3edf2abaae7842532cd80. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability is primarily a stability and availability issue, causing kernel panics and potential denial of service on affected devices running Samsung Exynos-based Linux kernels. The fix involves reordering the initialization sequence to set ctx->clk_data.num before dereferencing ctx->clk_data.hws, preventing the out-of-bounds access and subsequent crash.

For European organizations, the impact of CVE-2025-39728 depends largely on their use of Linux systems running on Samsung Exynos SoCs, which are commonly found in embedded devices, mobile platforms, and specialized hardware. Organizations deploying Linux-based IoT devices, industrial control systems, or mobile infrastructure that utilize Samsung Exynos chips could experience system instability or denial of service due to kernel panics triggered by this vulnerability. This may disrupt critical services, cause downtime, and impact operational continuity. While the vulnerability does not appear to allow privilege escalation or remote code execution, the resulting kernel panic can lead to availability issues and potential data loss if systems crash unexpectedly. European sectors such as telecommunications, manufacturing, and automotive industries that rely on embedded Linux systems may be particularly vulnerable. Additionally, organizations using custom Linux kernels with Samsung clock drivers in their infrastructure should be aware of this risk. The absence of known exploits reduces immediate threat levels, but the vulnerability's presence in kernel code necessitates prompt attention to avoid future exploitation or accidental crashes.

To mitigate CVE-2025-39728, organizations should: 1) Identify and inventory all Linux systems running Samsung Exynos SoCs or kernels containing the affected commit hash. 2) Apply the official Linux kernel patches that reorder the initialization in samsung_clk_init() to prevent out-of-bounds access. If official patches are not yet available, consider backporting the fix from the latest kernel source. 3) Test patched kernels in staging environments to ensure stability before deployment. 4) Monitor kernel logs for UBSAN or panic messages related to samsung_clk_init to detect potential exploitation or crashes. 5) For embedded or IoT devices, coordinate with hardware vendors and device manufacturers to obtain updated firmware or kernel versions incorporating the fix. 6) Implement robust system monitoring and automated reboot mechanisms to minimize downtime in case of unexpected kernel panics. 7) Restrict access to vulnerable devices and limit user privileges to reduce the risk of triggering the vulnerability through malicious or accidental means. 8) Maintain up-to-date inventories of kernel versions and hardware platforms to quickly respond to future vulnerabilities in similar subsystems.