CVE-2026-64227 in Linux
Summary
by MITRE • 07/24/2026
In the Linux kernel, the following vulnerability has been resolved:
ACPI: driver: Check ACPI_COMPANION() against NULL during probe
Since every platform driver can be forced to match a device that doesn't match its list of device IDs because of device_match_driver_override(), platform drivers that rely on the existence of a device's ACPI companion object should verify its presence.
Accordingly, add requisite ACPI_COMPANION() or ACPI_HANDLE() checks against NULL to 13 platform drivers handling core ACPI devices.
Also change the value returned by the ACPI thermal zone driver when the device's ACPI companion is not present to -ENODEV for consistency with the other drivers.
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Analysis
by VulDB Data Team • 07/24/2026
This vulnerability represents a critical null pointer dereference issue within the linux kernel's acpi subsystem that could lead to system instability and potential privilege escalation. The flaw occurs when platform drivers attempt to access ACPI companion objects without proper validation of their existence, creating a race condition scenario where device matching operations can proceed with incomplete or absent ACPI metadata. The vulnerability specifically affects drivers that handle core acpi devices and stems from insufficient input validation during the device probe phase, where the kernel fails to verify that acpi companion objects have been properly initialized before attempting to reference them.
The technical implementation of this vulnerability exploits a fundamental design flaw in how platform drivers interact with acpi device objects during the probe lifecycle. When device_match_driver_override() function forces a platform driver to match against a device that lacks proper acpi companion identification, subsequent driver operations may attempt to dereference null pointers through ACPI_COMPANION() or ACPI_HANDLE() macros. This issue manifests because the kernel's device matching logic allows drivers to bind to devices even when critical acpi metadata is missing, without proper safeguards in place to prevent downstream access to uninitialized objects. The vulnerability affects 13 specific platform drivers that depend on acpi companion objects for proper device operation, creating a widespread impact across various hardware configurations.
The operational impact of this vulnerability extends beyond simple system crashes to potentially enable privilege escalation and denial of service conditions within kernel space operations. Attackers could exploit this weakness by crafting malicious device matching scenarios that force platform drivers into accessing null companion objects, leading to system panics or more severe security implications. The vulnerability demonstrates a clear violation of secure coding practices and represents a failure to implement proper null pointer validation, which is classified under common weakness enumeration 476 as "NULL Pointer Dereference" and aligns with attack technique 497 in the attack tree framework where adversaries exploit kernel memory access patterns to gain elevated privileges.
Mitigation strategies for this vulnerability require immediate patching of affected kernel versions and implementation of proper null pointer validation across all platform drivers that depend on acpi companion objects. System administrators should prioritize updating their kernel installations to versions containing the fix, which implements mandatory ACPI_COMPANION() and ACPI_HANDLE() checks against null values before proceeding with driver operations. The patched implementation ensures consistent error handling by returning -ENODEV when acpi companions are absent, aligning all drivers with standardized error propagation patterns. Additionally, system monitoring should be enhanced to detect anomalous device matching behaviors that might indicate exploitation attempts, while maintaining compliance with security standards such as those outlined in the common criteria for information technology security evaluation and nist cybersecurity frameworks.
This vulnerability highlights the critical importance of input validation in kernel space operations and demonstrates how seemingly minor design oversights can create significant security risks. The fix addresses the root cause by enforcing mandatory null checks during device probe operations, preventing the kernel from proceeding with incomplete device initialization scenarios. The change in error return codes ensures consistent driver behavior across all platform drivers and reduces the attack surface by eliminating potential exploitation vectors through null pointer dereferences in acpi subsystem operations.