FreeRTOS Kernel flaw lets unprivileged tasks access privileged memory on Cortex-R82

A high-severity vulnerability in the FreeRTOS kernel allows unprivileged tasks to access privileged memory on specific Arm processors. The flaw, tracked as CVE-2026-109588, exists in versions 11.3.0 and 11.3.1 running on Arm Cortex-R82 systems with memory protection unit support.

What happened

The National Vulnerability Database records CVE-2026-109588 as a high-severity issue with a CVSS score of 8.8. The flaw stems from numeric truncation during buffer length validation within the MPU buffer authorization check. This defect is specific to the Arm Cortex-R82 processor using the Armv8-R AArch64 MPU port. It affects FreeRTOS-Kernel versions 11.3.0 and 11.3.1.

Under certain conditions, an unprivileged task can exploit this truncation error. The task can perform a stream buffer system call that bypasses the intended buffer window validation. This allows the task to read or write data in privileged kernel memory. The weaknesses are associated with CWE-197, CWE-787, and CWE-125.

Why it matters

This vulnerability compromises the memory isolation guarantees provided by the memory protection unit. In embedded systems, the MPU is critical for separating trusted kernel code from untrusted application tasks. Bypassing this check allows lower-privilege code to interact with higher-privilege memory regions.

Security teams managing industrial control systems or automotive electronics using these specific FreeRTOS versions are exposed. The ability to read or write privileged memory can lead to arbitrary code execution or system instability. The flaw requires specific conditions to trigger, but the impact is severe due to the loss of memory protection boundaries.

Our take on the response

The vendor has released a fix for this vulnerability. Users are advised to upgrade to FreeRTOS-Kernel version 11.3.2 or later. This update addresses the numeric truncation issue in the buffer authorization check. No other remediation steps, such as configuration changes or workarounds, are mentioned in the advisory.

What TO DO

• Identify all devices running FreeRTOS-Kernel versions 11.3.0 or 11.3.1.
• Verify if these devices utilize the Arm Cortex-R82 processor with MPU enabled.
• Plan an upgrade to version 11.3.2 or later to patch the vulnerability.
• Monitor system logs for unusual stream buffer system call activity during the transition.

What defenders should look for

Teams should monitor for anomalous memory access patterns in embedded systems using FreeRTOS. Look for unexpected system crashes or hangs that may indicate buffer overflows or unauthorized memory writes. Check for irregularities in stream buffer usage, particularly from unprivileged tasks. Investigate any signs of privilege escalation where low-level tasks interact with kernel memory. Implement strict input validation for buffer lengths in custom applications. Review MPU configuration logs for any bypass attempts or error conditions related to buffer authorization checks.

Background: Input validation

Input validation is the process of verifying that data entering a system matches expected formats, types, and ranges before processing. It prevents malicious payloads from executing code or crashing services. You must validate at every entry point, not just the user interface, because attackers bypass front-end checks entirely.

Read the full guide: What Is Input Validation: How to Stop Bad Data From Breaking Systems

What to do and how to stay safe: FreeRTOS

• Inventory all embedded devices to identify those running FreeRTOS-Kernel versions 11.3.0 or 11.3.1.
• Confirm whether these devices are built on the Arm Cortex-R82 processor with MPU enabled.
• Schedule an upgrade to FreeRTOS-Kernel version 11.3.2 or later to apply the vendor's fix.
• Monitor system behavior for signs of memory corruption or unexpected privilege escalation after any updates.

Step-by-step guide: Vulnerability Management Myths That Waste Your Time and Budget

General security guidance from the NetSec Tribune newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

Which FreeRTOS versions are affected by CVE-2026-109588?

FreeRTOS-Kernel versions 11.3.0 and 11.3.1 are affected by this vulnerability.

What is the severity rating for this CVE?

The National Vulnerability Database rates CVE-2026-109588 as high severity with a CVSS score of 8.8.

How can users remediate this vulnerability?

Users should upgrade to FreeRTOS-Kernel version 11.3.2 or later to fix the issue.