CVE-2026-72432 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
tpm_crb: Check ACPI_COMPANION() against NULL during probe
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(), so platform drivers that rely on the existence of a device's ACPI companion object need to verify its presence.
Accordingly, add a requisite ACPI_COMPANION() check against NULL to the tpm_crb driver.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability in question affects the Linux kernel's tpm_crb driver which handles communication with Trusted Platform Module controllers through the CRB (Command Response Buffer) interface. This issue represents a classic null pointer dereference scenario that could lead to system instability or potential privilege escalation. The problem stems from insufficient validation of ACPI companion objects during device probe operations, creating a condition where drivers might attempt to access memory locations that have not been properly initialized.
The technical flaw manifests when the tpm_crb driver processes platform devices without first verifying that the expected ACPI companion object exists. The device_match_driver_override() function in the kernel's device matching framework can force a platform driver to bind to a device even when the device ID list doesn't explicitly match, but this mechanism does not guarantee the presence of required companion objects. This creates a race condition or initialization gap where the driver assumes an ACPI companion object exists and attempts to dereference it without proper NULL checking.
This vulnerability has significant operational impact within embedded systems and server environments that rely on TPM functionality for security operations such as secure boot, hardware-based encryption key storage, and system integrity measurement. The null pointer dereference could result in kernel panics, system crashes, or more insidiously allow attackers to manipulate the device binding process to achieve unauthorized access to TPM resources. From a cybersecurity perspective, this represents a privilege escalation vector that could undermine the security foundation of systems relying on hardware-based security features.
The fix implemented addresses the core issue by adding explicit ACPI_COMPANION() NULL checks before any operations that depend on the companion object's existence. This follows established best practices for defensive programming and aligns with CWE-476 which identifies null pointer dereference as a critical weakness in software systems. The mitigation strategy directly addresses the root cause rather than attempting to patch symptoms, ensuring that platform drivers properly validate their environment before proceeding with operations that assume certain device properties exist.
From an ATT&CK framework perspective, this vulnerability could be leveraged during initial access phases or privilege escalation attempts where adversaries seek to manipulate system boot processes or hardware security features. The fix demonstrates proper input validation and error handling practices that should be applied across all kernel drivers dealing with platform-specific device objects. This type of vulnerability is particularly concerning in enterprise environments where TPM functionality is critical for maintaining system integrity and protecting sensitive cryptographic operations from tampering.
The resolution ensures that the tpm_crb driver properly validates device compatibility before attempting to establish communication channels with TPM hardware, preventing potential exploitation scenarios while maintaining full functional compatibility for legitimate use cases. This approach aligns with security by design principles and represents a mature defensive strategy against common kernel-level vulnerabilities that could compromise system security foundations.