CVE-2024-44951 is a vulnerability identified in the Linux kernel's serial driver for the SC16IS7XX family of UART (Universal Asynchronous Receiver/Transmitter) devices. The issue arises from a regression introduced by a specific commit (4409df5866b7), which altered the locking mechanism from a chip-wide lock to a per-channel lock on the Enhanced Feature Register (EFR). This change inadvertently compromised the protection of the shared data buffer used by both transmit (Tx) and receive (Rx) handlers across multiple channels of the integrated circuit (IC). The vulnerability manifests when a packet is received on one channel (channel A) nearly simultaneously as a packet is transmitted on another channel (channel B). Due to the flawed locking, data from the received packet on channel A can corrupt the transmit buffer of channel B, causing the wrong data to be transmitted. This buffer corruption can lead to data integrity issues in serial communications, potentially causing communication failures, data leakage between channels, or unexpected behavior in systems relying on these serial interfaces. The fix involves two key changes: first, switching to the use of kfifo_out_linear_ptr() in the transmission handler to remove the dependency on a shared Rx/Tx buffer; second, replacing the chip-wide Rx buffer with separate Rx buffers for each channel, thereby restoring proper isolation and synchronization. This vulnerability is specific to certain Linux kernel versions containing the problematic commit and affects systems utilizing the SC16IS7XX serial driver. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2024-44951 depends largely on the deployment of Linux systems using the SC16IS7XX serial driver, which is common in embedded systems, industrial control systems (ICS), IoT devices, and specialized communication equipment. The corruption of transmit buffers can lead to data integrity failures, causing miscommunication between devices, operational disruptions, or potential data leakage across communication channels. In critical infrastructure sectors such as manufacturing, energy, transportation, and healthcare, where embedded Linux devices are prevalent, this could result in system malfunctions or degraded operational reliability. Although no direct remote code execution or privilege escalation is indicated, the vulnerability could be exploited to disrupt communications or cause denial of service conditions in serially connected devices. This may affect automation processes, sensor data accuracy, or control commands, potentially leading to safety risks or operational downtime. Given the lack of known exploits, the immediate risk is moderate, but the vulnerability should be addressed promptly to prevent future exploitation, especially in environments where serial communication integrity is critical.

To mitigate CVE-2024-44951, organizations should: 1) Apply the official Linux kernel patches that fix the regression by implementing separate Rx buffers per channel and using kfifo_out_linear_ptr() to handle Tx buffers correctly. 2) Identify and inventory all devices running affected Linux kernel versions with the SC16IS7XX driver, prioritizing embedded and industrial systems. 3) Where patching is not immediately feasible, consider isolating affected devices from critical networks or limiting their communication to trusted endpoints to reduce risk. 4) Monitor serial communication logs and device behavior for anomalies indicative of buffer corruption or data misrouting. 5) Collaborate with device vendors to ensure firmware updates incorporate the kernel fixes. 6) Implement strict change management and testing procedures for kernel updates in embedded environments to avoid regressions. 7) For new deployments, prefer Linux kernel versions that have resolved this issue and validate serial driver behavior under concurrent Tx/Rx loads.