CVE-2026-31729 is a high-severity vulnerability in the Linux kernel's USB Type-C UCSI driver. It involves improper validation of the connector number extracted from the Connector Change Indicator (CCI). The connector number is a 7-bit field but can be out-of-range relative to the allocated connector array, potentially causing out-of-bounds array access. This flaw could be triggered by a malicious or malfunctioning device reporting an invalid connector number. The issue has been resolved by adding a bounds check in the ucsi_notify_common() function to reject invalid connector numbers early.