CVE-2023-54118: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54118 is a race condition vulnerability in the Linux kernel's sc16is7xx serial driver affecting GPIO controller initialization. The flaw occurs because the GPIO controller is set up too early during the driver probe sequence, allowing another device to attempt to use GPIO lines before the sc16is7xx device has finished initializing. This results in a kernel Oops (crash) when GPIO lines are configured. The vulnerability was published on December 24, 2025, and has a CVSS v3.1 base score of 5.5 (Medium) (Red Hat CVE, Red Hat Bugzilla).

The root cause is a race condition (CWE-362) in the sc16is7xx driver's probe function, where the GPIO controller subsystem is registered before the device has completed full initialization. When another driver (e.g., gpio_led) attempts to configure GPIO lines via gpiod_direction_output during its own probe, it calls into sc16is7xx_gpio_direction_output, which reads from uninitialized or invalid memory, triggering an "Unable to handle kernel read from unreadable memory" Oops. The attack vector is local, requiring low privileges, and exploitation is contingent on the presence of a dependent GPIO consumer device probing concurrently. The fix moves the GPIO controller registration to later in the probe function and reorders error handling accordingly (Red Hat Bugzilla).

Successful triggering of this vulnerability causes a kernel Oops, resulting in a denial-of-service condition — system instability, a potential hang, or a kernel panic — on systems using the sc16is7xx serial-to-GPIO driver with dependent GPIO consumer devices. There is no impact on confidentiality or integrity; the vulnerability is limited to availability. Affected systems are typically embedded Linux platforms or systems with SC16IS7xx UART/GPIO bridge chips (Red Hat CVE).

The recommended remediation is to update to a patched version of the Linux kernel that includes the fix moving GPIO controller setup to later in the sc16is7xx probe function. Patch commits are available in the stable kernel tree (e.g., commits 17b96b5c19be, 49b326ce8a68, b71ff2067078, c8f71b49ee4d). As a temporary workaround, administrators can restrict local user access on systems using the sc16is7xx driver and monitor kernel logs for unexpected Oops or crash events. Verifying the kernel module initialization sequence on affected embedded systems is also advised (Red Hat Bugzilla).