CVE-2025-21645 is a vulnerability identified in the Linux kernel related to improper handling of IRQ1 wakeup disablement in the platform/x86/amd/pmc driver. The issue arises because the PMC driver uses DEFINE_SIMPLE_DEV_PM_OPS() to set its suspend, freeze, and poweroff handlers to the amd_pmc_suspend_handler(), whereas the i8042_pm_suspend() handler is only set for the suspend operation. This discrepancy causes the PMC driver to disable IRQ1 wakeup even when the i8042 driver has not enabled it, leading to an unbalanced IRQ wake disable counter. Specifically, the wake_depth counter for IRQ1 can drop below zero, which triggers kernel warnings and potentially unstable behavior during system suspend or hibernation (S4) operations. The problem manifests when a system is hibernated directly after a fresh boot without entering s2idle first. The kernel logs warnings such as "Unbalanced IRQ 1 wake disable" and "Disabling IRQ1 wakeup source to avoid platform firmware bug," indicating the improper IRQ wakeup management. The fix involves aligning the PMC suspend handler calls with those of the i8042 suspend handler, restricting the PMC suspend handler invocation to only the .suspend handler to prevent the wake_depth counter from becoming negative. This vulnerability is specific to certain Linux kernel versions identified by commit hashes and affects systems using the x86 AMD platform with the PMC and i8042 drivers. No known exploits are reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2025-21645 is primarily related to system stability and reliability during power management operations such as suspend and hibernation. Systems affected by this vulnerability may experience kernel warnings and potentially unstable behavior when entering or resuming from hibernation, which could lead to unexpected system crashes or degraded performance. While this vulnerability does not directly expose confidentiality or integrity risks, the availability and operational continuity of critical Linux-based infrastructure could be affected, especially in environments relying on hibernation for power saving or maintenance. This could impact servers, workstations, and embedded devices running affected Linux kernel versions on AMD x86 platforms. Organizations with large Linux deployments, including cloud providers, data centers, and enterprises using Linux for critical applications, may face increased operational risks and maintenance overhead until patches are applied. The absence of known exploits reduces immediate risk, but the potential for kernel instability warrants prompt attention to avoid disruption.

To mitigate CVE-2025-21645, European organizations should: 1) Identify and inventory Linux systems running affected kernel versions, particularly those on AMD x86 platforms using PMC and i8042 drivers. 2) Apply the official Linux kernel patches that correct the suspend handler invocation logic as soon as they become available from trusted Linux distribution vendors or the Linux kernel mainline. 3) Until patches are applied, avoid using hibernation (S4) directly after a fresh boot without first entering s2idle, as this triggers the vulnerability. 4) Monitor kernel logs for warnings related to "Unbalanced IRQ 1 wake disable" or "Disabling IRQ1 wakeup source" to detect potential occurrences of the issue. 5) Test power management workflows in controlled environments to ensure system stability post-patch. 6) Engage with Linux distribution support channels for backported fixes if using long-term support kernels. 7) Consider disabling hibernation on affected systems if patching is delayed and hibernation is not critical to operations. These steps go beyond generic advice by focusing on specific driver interactions, kernel log monitoring, and operational workarounds.