CVE-2023-52456 is a vulnerability identified in the Linux kernel's serial driver for the i.MX platform, specifically affecting the RS485 serial port implementation. The issue arises in the transmission state machine controlling the RTS pin, which drives the TX_EN pin of the RS485 transceiver. When a TTY port is closed abruptly during an ongoing transmission—such as when a userland application crashes—the imx_uart_shutdown function disables the interface and the Transmission Complete (TC) interrupt. Subsequently, imx_uart_stop_tx detects an incomplete transmission and attempts to bail out, expecting the TC interrupt to retrigger the transmission state machine. However, since the TC interrupt is disabled, the state machine remains stuck in the SEND state, causing a deadlock. This deadlock results in the TX_EN pin remaining low, effectively rendering the RS485 interface non-functional. The patch resolves this by modifying imx_uart_stop_tx to verify both the presence of an incomplete transmission and whether the TC interrupts are enabled before bailing. This ensures the state machine properly transitions to the WAIT_AFTER_SEND state, restoring correct operation after an interrupted transmission. This vulnerability is specific to the Linux kernel versions containing the affected commit hashes and impacts systems using the i.MX UART driver for RS485 communication. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2023-52456 primarily concerns industrial and embedded systems relying on Linux-based devices with i.MX processors using RS485 serial communication. RS485 is commonly used in industrial automation, building management systems, and critical infrastructure for reliable serial communication over long distances. A deadlock in the transmission state machine could lead to loss of communication capabilities, causing operational disruptions, data transmission failures, or downtime in automated processes. While this vulnerability does not directly lead to privilege escalation or remote code execution, the loss of RS485 communication can impact system availability and reliability, potentially affecting manufacturing lines, energy distribution, or transportation control systems. The absence of known exploits and the requirement for a specific hardware and software configuration limit the immediate risk; however, organizations with critical RS485-dependent infrastructure should prioritize patching to avoid operational interruptions.

To mitigate CVE-2023-52456, European organizations should: 1) Identify all Linux systems using i.MX processors with RS485 serial ports, particularly those running affected kernel versions. 2) Apply the official Linux kernel patches or upgrade to a kernel version where this vulnerability is resolved. 3) For embedded or industrial devices where kernel upgrades are challenging, coordinate with device vendors for firmware updates incorporating the fix. 4) Implement monitoring for RS485 communication failures or unexpected port closures that could indicate the deadlock condition. 5) Establish robust application-level error handling to gracefully manage TTY port closures and avoid abrupt terminations during transmissions. 6) Conduct thorough testing in staging environments to ensure that the patch does not disrupt existing RS485 communication workflows. 7) Maintain an inventory of critical systems using RS485 to prioritize patch deployment and reduce operational risk.