CVE-2026-93132 in Linux
Summary
by MITRE • 09/18/2026
In the Linux kernel, the following vulnerability has been resolved:
ACPI: RISC-V: Fix riscv_acpi_add_prt_dep() loop handling
The loop in riscv_acpi_add_prt_dep() includes error conditions that are handled in a dubious - if not outright wrong - way, by continuining the loop (which skips and misses the entry pointer update to point to the next entry).
Rewrite the loop as a for loop (that handles the continuation correctly) and wrap the condition and update statements using helper functions to make it cleaner.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified in the Linux kernel involves a logic error within the ACPI subsystem specifically affecting RISC-V architecture implementations, located in the function riscv_acpi_add_prt_dep(). This function is responsible for processing dependency lists associated with Peripheral Resource Table entries during system initialization and device enumeration. The core technical flaw stems from improper loop control flow when handling specific error conditions or boundary cases within the iteration over ACPI descriptor structures. Specifically, the original implementation utilized a while loop structure where certain conditional branches resulted in continuing to the next iteration without correctly advancing an internal pointer that tracks the current position within the ACPI data buffer. This oversight means that after encountering an error condition or completing a processing step under specific circumstances, the iterator fails to update its reference to point to the subsequent entry in the sequence.
This incorrect handling of the loop continuation leads directly to memory access anomalies and potential denial of service scenarios during system boot or device hot-plug events. Because the pointer is not advanced correctly, the kernel may either re-process the same ACPI descriptor multiple times causing redundant operations and performance degradation, or more critically, it may fail to process subsequent valid entries in the dependency list. In severe cases, if the loop logic becomes confused due to stale pointers, it could lead to out-of-bounds memory reads as the iterator attempts to access data beyond the intended buffer boundaries based on incorrect assumptions about the structure layout and current position. This represents a classic instance of improper resource management within low-level kernel code where precise pointer arithmetic is critical for system stability.
From a classification perspective, this vulnerability aligns with CWE-787: Out-of-bounds Read, as the failure to update the entry pointer can result in reading memory outside the allocated ACPI buffer region depending on how subsequent iterations are calculated relative to the end of the data structure. Additionally, it relates to CWE-691: Use of Less Than One Offset Allowed if the loop logic allows for negative or zero offsets due to incorrect state management. In terms of attack vectors and behavioral patterns, this type of flaw is relevant to ATT&CK technique T1053: Scheduled Task/Job, specifically in the context of system initialization scripts that rely on accurate ACPI table parsing to configure hardware correctly. While not directly exploitable for remote code execution by an external attacker without physical access or privileged local privileges, it poses a significant risk to system reliability and availability during critical boot sequences where ACPI tables are parsed to establish device drivers and power management states.
The remediation strategy implemented involves refactoring the loop structure from a while-based iteration to a more robust for-loop construct that explicitly manages initialization, condition checking, and increment operations in a standardized manner. This structural change ensures that pointer advancement is decoupled from conditional error handling logic, thereby eliminating the possibility of skipping necessary updates. Furthermore, the solution incorporates helper functions to encapsulate complex conditions and update statements, improving code readability and reducing the likelihood of future logical errors during maintenance or extension of this subsystem. By enforcing strict adherence to loop invariants through cleaner control flow structures, the kernel ensures that every ACPI descriptor entry is processed exactly once with correct pointer progression regardless of intermediate error states encountered during parsing.
Mitigation for organizations running affected Linux kernels involves applying upstream kernel patches as soon as they are available through standard distribution update channels. For systems where immediate patching is not feasible due to stability concerns, administrators should monitor system logs for ACPI-related errors or unexpected device enumeration failures during boot processes. Since this vulnerability primarily affects the RISC-V architecture implementation of the ACPI subsystem, mitigation efforts can be focused on verifying that all peripheral dependencies are correctly resolved after updates. Long-term prevention requires rigorous code review practices emphasizing pointer arithmetic validation and loop invariant verification in low-level system components to prevent similar logic errors from being introduced into critical infrastructure software.