CVE-2026-77236 in FreeRTOS
Summary
by MITRE • 08/21/2026
Missing minimum size validation in secure context allocation in FreeRTOS-Kernel before 11.3.1 might allow local users to corrupt secure-world heap metadata via an out-of-bounds write with an undersized stack size parameter. To remediate this issue, users should upgrade to version 11.3.1 or later.
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Analysis
by VulDB Data Team • 08/21/2026
The vulnerability identified in FreeRTOS-Kernel prior to version 11.3.1 represents a critical flaw within the secure context allocation mechanism, specifically affecting systems that utilize TrustZone technology for hardware-based security isolation. This issue stems from an insufficient validation of input parameters during the initialization or configuration of secure contexts. When a local user or application provides an undersized stack size parameter to the kernel's memory management routines responsible for allocating space in the secure world heap, the system fails to enforce minimum boundary checks. Consequently, this oversight allows for an out-of-bounds write operation where data intended for the context structure overflows into adjacent memory regions that contain critical heap metadata structures.
From a technical perspective, the core of this vulnerability lies in the absence of rigorous bounds checking before memory allocation and subsequent writes occur within the secure address space. In embedded systems utilizing FreeRTOS with TrustZone support, the separation between normal world and secure world is maintained through specific hardware registers and memory partitions. The heap metadata manages how free blocks are tracked to facilitate dynamic memory allocation. When an out-of-bounds write corrupts this metadata, it disrupts the integrity of the allocator's internal state. This corruption can lead to unpredictable behavior in subsequent memory operations, potentially allowing an attacker who controls the input parameters to manipulate pointer values or size fields within the heap structure. Such manipulation is a precursor to more severe exploits, including arbitrary code execution or complete compromise of the secure environment if the corrupted metadata leads to the allocation of maliciously crafted buffers that overwrite executable code or sensitive security keys stored in adjacent memory locations.
The operational impact of this vulnerability is significant for any deployment relying on FreeRTOS-Kernel versions earlier than 11.3.1, particularly those implementing ARM TrustZone architecture. Local users with access to the kernel interfaces can trigger this condition by passing crafted stack size values during context creation or modification operations. The immediate consequence is memory corruption within the secure world heap, which undermines the confidentiality and integrity guarantees provided by hardware security modules. In worst-case scenarios, an attacker could leverage this metadata corruption to bypass security boundaries, escalate privileges from a less privileged domain to the highly trusted monitor mode or secure OS environment, and exfiltrate sensitive data such as cryptographic keys or authentication tokens that are protected under normal circumstances by the isolation mechanisms of TrustZone.
This flaw aligns with Common Weakness Enumeration (CWE) category CWE-120, which describes buffer copy without checking size limits, specifically manifesting here as a heap-based out-of-bounds write due to missing validation. It also relates to CWE-682 regarding incorrect calculation of the number of elements in an array or structure when determining allocation sizes. In terms of adversary tactics and techniques, this vulnerability facilitates initial access and privilege escalation within ATT&CK frameworks by allowing local attackers to compromise system integrity through memory corruption exploits that bypass standard security controls designed for embedded environments. The lack of input validation is a fundamental design flaw that undermines the trust boundary between software components operating at different security levels.
To remediate this issue, organizations must upgrade FreeRTOS-Kernel to version 11.3.1 or any later release where the developers have implemented strict minimum size validations and bounds checking for secure context allocations. Until an upgrade is feasible, mitigation strategies should focus on restricting access to the affected kernel APIs by ensuring that only trusted applications with verified input parameters can invoke these functions. Implementing runtime memory protection features such as Memory Protection Unit (MPU) configurations can help limit the impact of potential out-of-bounds writes by preventing execution or write access to unauthorized memory regions, although this is a compensatory control rather than a fix for the root cause. Regular security audits and static code analysis focused on input validation in kernel-level functions are recommended to detect similar vulnerabilities in other parts of the embedded software stack before they can be exploited in production environments.