CVE-2026-53116 describes a use-after-free (UAF) vulnerability in the Linux kernel's s390 architecture AP bus driver_override handling. When AP masks are updated, a function accesses the driver_override field without holding a lock, racing against concurrent modifications that may free the old string, causing a potential UAF. The fix involves using the generic driver_override infrastructure that protects accesses with an internal spinlock. Unlike other buses, the AP bus checks driver_override in ap_device_probe() and __ap_revise_reserved(), not in the match() callback. This vulnerability affects Linux kernel versions prior to 7.0.0-28.28 and related variants.

Successful exploitation could lead to memory corruption due to use-after-free, potentially resulting in privilege escalation or system compromise. The CVSS v3.1 score is 7.8 (high), reflecting local attack vector with low complexity, requiring low privileges, no user interaction, and impacting confidentiality, integrity, and availability. However, no known exploits are reported in the wild.

A patch is available and included in Linux kernel updates version 7.0.0-28.28 and later. Users should apply the official kernel updates provided by their Linux distribution (e.g., Ubuntu) and reboot the system to activate the fixes. Due to an ABI change, recompilation and reinstallation of third-party kernel modules may be required. No additional mitigation is indicated by the vendor advisory.