CVE-2020-36778 is a vulnerability identified in the Linux kernel's I2C subsystem, specifically within the xiic driver implementation. The issue arises from improper handling of the power management (PM) runtime reference count when the function pm_runtime_get_sync fails. Normally, pm_runtime_get_sync increments the PM reference count to indicate that a device is in use, preventing it from being powered down prematurely. However, in this case, even when pm_runtime_get_sync fails, it still increments the reference count, which is unexpected behavior. The xiic_xfer and xiic_i2c_remove functions do not properly account for this increment on failure, leading to a reference leak. This leak means that the PM usage counter becomes unbalanced, potentially preventing the device from entering low power states or causing resource management issues. The fix involves replacing pm_runtime_get_sync with pm_runtime_resume_and_get, which correctly balances the usage counter by only incrementing it when appropriate. This vulnerability is a resource management bug rather than a direct memory corruption or code execution flaw. It does not appear to allow privilege escalation or arbitrary code execution. No known exploits are reported in the wild, and the vulnerability primarily affects Linux kernel versions containing the xiic driver with the described behavior. The vulnerability was published on February 28, 2024, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2020-36778 is primarily related to system stability and power management efficiency rather than direct security compromise. Devices relying on the xiic I2C driver in the Linux kernel may experience increased power consumption or failure to enter low power states due to the reference leak. This can lead to degraded performance, reduced battery life in embedded or mobile devices, and potential system resource exhaustion over time. In critical infrastructure or industrial control systems that use Linux-based embedded devices with I2C peripherals, this could cause unexpected device behavior or downtime. However, since the vulnerability does not enable remote code execution or privilege escalation, the confidentiality and integrity of data are unlikely to be directly affected. The absence of known exploits reduces immediate risk, but unpatched systems may face operational inefficiencies and increased maintenance costs.

European organizations should prioritize updating their Linux kernel to versions where this vulnerability is patched, specifically ensuring that the xiic driver uses pm_runtime_resume_and_get instead of pm_runtime_get_sync in the affected code paths. For embedded systems or devices where kernel updates are challenging, organizations should monitor device power management behavior and consider workarounds such as disabling runtime PM for affected devices if feasible, though this may impact power efficiency. Additionally, organizations should implement robust patch management processes to ensure timely application of kernel updates. Monitoring system logs for unusual power management warnings or errors related to I2C devices can help detect potential issues stemming from this vulnerability. Collaboration with hardware vendors to confirm device compatibility with patched kernels is also recommended to avoid regressions.