CVE-2026-53115: Linux Kernel fsl-mc Use-After-Free Privilege Escalation

Technical summary

CVE-2026-53115 is a use-after-free (UAF) vulnerability in the Linux kernel's fsl-mc bus implementation. During __driver_attach() execution, the bus match() callback accesses the driver_override field without device lock protection. While the kernel intentionally calls match() unlocked for performance reasons, the fsl-mc driver failed to use the driver-core's thread-safe driver_override infrastructure, allowing concurrent access patterns that can cause UAF. The fix adopts the generic driver_override mechanism, which provides internal locking and safe field access.

Business impact

Successful exploitation allows a local, authenticated user to execute arbitrary code with kernel privileges. This can lead to complete system compromise, including unauthorized data access, system manipulation, and lateral movement within affected infrastructure. Organizations running vulnerable Linux kernels on systems with fsl-mc hardware (primarily NXP/Freescale platforms) face elevated risk of privilege escalation attacks.

Affected systems

The vulnerability affects the Linux kernel in the fsl-mc bus driver component. This impacts systems using Freescale/NXP management complex hardware, particularly embedded and ARM-based platforms. The vulnerability requires local access and an authenticated user context, limiting exposure to systems where untrusted local users may be present. Verify your kernel version and fsl-mc driver status against the official Linux kernel patch advisories.

Exploitability

Exploitation requires local access and authentication on the target system; remote exploitation is not possible. The vulnerability is readily exploitable by a local user with standard privileges due to the straightforward race condition. However, successful exploitation depends on precise timing to trigger the UAF condition. The CVSS 3.1 score of 7.8 (HIGH) reflects the local requirement but acknowledges significant impact potential across confidentiality, integrity, and availability.

Remediation

Apply the Linux kernel patch that migrates the fsl-mc driver to use the generic driver_override infrastructure provided by the driver core. This ensures proper locking is maintained around driver_override field access. Update your kernel to a version containing the fix—verify the specific patched kernel version from your Linux distribution's security advisories and kernel maintainers' release notes.

Patch guidance

Obtain and deploy the corrected Linux kernel version from your distribution's repositories. Most major distributions (Red Hat, Debian, Ubuntu, SUSE) will backport this fix to supported kernel branches. For custom or enterprise kernels, apply the upstream patch directly and recompile. Verify patch application by confirming the fsl-mc driver uses the driver-core's driver_override mechanism. Kernel reboot is required to activate the fix. Test in a staging environment before production deployment.

Detection guidance

Monitor kernel logs for fsl-mc bus driver errors or unexpected behavior during driver probing. Use kernel debugging tools (kprobes, ftrace) to observe driver_override field access patterns on systems with fsl-mc hardware. Implement firmware-level monitoring for unexpected privilege escalation attempts from local users. Audit process execution logs for suspicious activities by authenticated local users on affected systems. Note that this vulnerability is difficult to detect via external observables; patch deployment is the primary control.

Why prioritize this

This vulnerability merits rapid patching due to its HIGH severity, local privilege escalation potential, and straightforward exploitability. While it requires authentication and local access, it affects the kernel's core driver binding mechanism and can grant full system compromise. Prioritize systems where untrusted local users have access, or where fsl-mc hardware is deployed in security-sensitive roles.

Risk score, explained

CVSS 3.1 score of 7.8 reflects: Attack Vector (Local)—requires system access; Attack Complexity (Low)—race condition is reliably triggered; Privileges Required (Low)—standard user context suffices; User Interaction (None)—automatic exploitation is possible; and maximum impact across Confidentiality, Integrity, and Availability (all High). The HIGH severity is appropriate for kernel-level privilege escalation vulnerabilities, though the local access requirement prevents a critical rating.

Frequently asked questions