CVE-2026-93133 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
ACPI: RISC-V: Check acpi_get_handle() status in riscv_acpi_add_prt_dep()
In riscv_acpi_add_prt_dep(), the acpi_get_handle() call can fail which would leave link_handle uninitialized.
Fix it by checking the acpi_get_handle() return status and skip the entry if it fails.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel's Advanced Configuration and Power Interface implementation for RISC-V architectures contains a logic flaw within the riscv_acpi_add_prt_dep function that can lead to undefined behavior or system instability. This specific vulnerability arises from an insufficient validation of return values during device dependency resolution processes. The ACPI subsystem is responsible for managing hardware configuration, power management, and thermal data across various platforms, including RISC-V systems where it serves as a critical abstraction layer between the operating system and firmware-provided hardware descriptions. When the kernel attempts to resolve dependencies for Peripheral Reference Table entries, it relies on retrieving valid handles that represent specific ACPI objects within the namespace.
The core technical flaw lies in the handling of the acpi_get_handle function call. This function is designed to retrieve a handle associated with an ACPI object identified by its path name. However, like many low-level system calls, it can fail due to various reasons such as malformed ACPI tables, missing objects in the namespace, or corrupted data structures provided by firmware. In the original implementation of riscv_acpi_add_prt_dep, there was no check on the return status of acpi_get_handle. Consequently, if this function returned an error code indicating failure, the variable intended to store the resulting link handle remained uninitialized. This is a classic instance of using an uninitialised local variable, which falls under CWE-457 in the Common Weakness Enumeration taxonomy.
The operational impact of leaving the link_handle uninitialized can be severe depending on how subsequent code utilizes this value. In C programming languages like that used by the Linux kernel, reading from an uninitialized memory location results in undefined behavior. The garbage data present in the stack or register space where link_handle resides could be interpreted as a valid pointer address. If this invalid pointer is subsequently dereferenced to access ACPI device structures or modify dependency links, it can lead to a kernel panic due to accessing unmapped memory pages. Alternatively, if the random value happens to point to writable but unintended memory regions, it could result in data corruption of critical kernel structures. In worst-case scenarios involving sophisticated exploitation techniques where an attacker can influence surrounding stack contents, this flaw might theoretically be leveraged for arbitrary code execution or privilege escalation, although such outcomes depend heavily on specific compiler optimizations and runtime conditions.
This vulnerability is categorized under CWE-457 which addresses the use of uninitialised variables, a common source of bugs in systems programming that often leads to crashes or security breaches. From an attack surface perspective, this aligns with MITRE ATT&CK technique T1059 related to command and script interpreters if it allows for further exploitation leading to code execution, though primarily it represents a stability issue rather than a direct remote exploit vector unless combined with other vulnerabilities in the ACPI parsing pipeline. The flaw highlights the importance of defensive programming practices within kernel development where assumptions about data validity must always be explicitly verified before use.
To mitigate this vulnerability, developers have implemented a check on the return status of acpi_get_handle immediately after its invocation. If the function indicates failure by returning an error code rather than success, the processing for that specific entry is skipped entirely. This prevents the uninitialized variable from being propagated further into the dependency resolution logic. By ensuring that only valid handles are processed, the kernel maintains memory safety and structural integrity of ACPI device relationships. System administrators should ensure their systems are updated with patches containing this fix to prevent potential instability during boot sequences or runtime power management operations on RISC-V platforms relying on ACPI for hardware configuration. Regular auditing of return values from low-level API calls is essential to maintain robustness in operating system kernels.