CVE-2026-109588 in FreeRTOS
Summary
by MITRE • 10/16/2026
Numeric truncation of the buffer length in the MPU buffer authorization check in FreeRTOS-Kernel V11.3.0 and V11.3.1 on the Arm Cortex-R82 (Armv8-R AArch64) MPU port might allow, under certain conditions, an unprivileged task on MPU-enabled builds to read or write privileged kernel memory beyond the validated buffer window, via a stream buffer system call.
To remediate this issue, users should upgrade to version V11.3.2 or later.
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Analysis
by VulDB Data Team • 10/16/2026
The vulnerability identified in FreeRTOS-Kernel versions 11.3.0 and 11.3.1 represents a critical memory safety flaw within the Memory Protection Unit (MPU) authorization logic, specifically affecting builds configured for the Arm Cortex-R82 processor running in AArch64 mode. This issue stems from a numeric truncation error during the validation of buffer lengths when performing MPU region checks. In embedded systems utilizing an MPU, strict boundaries are enforced to isolate tasks and prevent unauthorized access to memory regions reserved for privileged kernel operations or other secure contexts. The core technical failure occurs because the length parameter provided by an unprivileged task is not correctly validated against the available address space before being used in calculations that determine the upper bound of a permitted memory region. Due to integer truncation, a larger buffer size requested by the application can be incorrectly interpreted as a smaller value, causing the MPU configuration logic to establish a protection window that extends significantly beyond the intended safe boundary.
This architectural flaw allows an unprivileged task to exploit the misconfigured MPU regions via stream buffer system calls. Stream buffers are commonly used for inter-task communication and data transfer within FreeRTOS environments. When such a call is made, the kernel checks whether the memory access falls within the authorized range defined by the MPU. Because of the truncation bug, the calculated upper limit of this range is erroneously expanded. Consequently, an attacker controlling or influencing the input to these stream buffer operations can craft requests that result in read or write accesses to privileged kernel memory located just beyond the validated window. This bypasses the hardware-enforced isolation mechanisms designed to protect critical system data structures from user-space interference, effectively neutralizing one of the primary security guarantees provided by MPU-based segmentation on Arm Cortex-R processors.
The operational impact of this vulnerability is severe, as it compromises both confidentiality and integrity within the embedded operating system environment. An unprivileged task gaining access to privileged kernel memory can potentially exfiltrate sensitive cryptographic keys, session tokens, or other confidential data stored in kernel space, leading to a significant breach of confidentiality. Furthermore, by writing to these protected regions, an attacker could corrupt critical kernel state variables, modify function pointers, or alter interrupt vectors. Such modifications can lead to arbitrary code execution with elevated privileges, denial of service through system crashes, or complete compromise of the device's security posture. In safety-critical applications where FreeRTOS is frequently deployed, such as automotive control units or industrial automation systems, this could result in unpredictable behavior and potential physical harm depending on the controlled processes.
From a classification perspective, this vulnerability aligns with CWE-190 Integer Overflow or Wraparound, specifically manifesting through truncation during type conversion or arithmetic operations that fail to account for full range validity before memory access checks are performed. It also relates closely to CWE-274 Improper Handling of Insufficient Permissions, as the flaw allows an entity without sufficient privileges to bypass permission controls enforced by hardware mechanisms. In terms of adversary tactics, this exploitation vector corresponds to ATT&CK technique T1055 Process Injection or more broadly to privilege escalation methods that leverage memory corruption flaws in operating system kernels. The attack requires local access and typically involves manipulating stream buffer inputs, which may be facilitated through maliciously crafted network packets if the device exposes such interfaces without adequate validation at higher protocol layers.
To remediate this issue, users must upgrade FreeRTOS-Kernel to version 11.3.2 or any subsequent release where the MPU authorization logic has been corrected to properly handle buffer length validations on Arm Cortex-R84 and similar architectures. Beyond immediate patching, developers should enforce strict input validation for all parameters passed to kernel system calls, particularly those involving memory allocation or boundary calculations. Implementing static analysis tools capable of detecting integer truncation issues during the build process can help identify similar vulnerabilities in custom code. Additionally, enabling compiler flags that detect overflow conditions and utilizing runtime bounds checking where performance permits adds layers of defense-in-depth. For systems relying on MPU for security isolation, regular audits of memory region configurations and rigorous testing of edge cases in buffer handling routines are essential to maintain the integrity of the trust boundary between unprivileged tasks and privileged kernel space.