CVE-2026-77235 in FreeRTOS
Summary
by MITRE • 08/21/2026
Missing privilege verification in the secure context cleanup handler in FreeRTOS-Kernel before 11.3.1 might allow local users to cause a use-after-free condition in secure-world memory via the SVC handler for secure context deallocation. To remediate this issue, users should upgrade to version 11.3.1 or later.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
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 operating system's handling of secure context cleanup operations, specifically targeting environments that utilize TrustZone technology for hardware-based isolation between normal and secure worlds. In such architectures, the kernel must manage state transitions carefully when switching execution contexts between these two distinct security domains. The core technical deficiency lies in the absence of proper privilege verification during the secure context deallocation process. When a system call is invoked to clean up or free resources associated with a secure context, the handler responsible for this operation fails to adequately verify that the calling entity possesses the requisite privileges to perform such an action on behalf of another task or within a specific security boundary. This oversight allows local users, who may have limited access rights in the normal world but can trigger system calls via Supervisor Call instructions, to manipulate the flow of execution into secure-world memory management routines without proper authorization checks.
This lack of verification directly facilitates a use-after-free condition within the secure-world memory space. A use-after-free vulnerability occurs when software continues to use a pointer after it has been freed, which can lead to undefined behavior, data corruption, or arbitrary code execution. In this specific scenario, by exploiting the missing privilege check in the SVC handler for secure context deallocation, an attacker can cause the system to free memory that is still referenced or expected to be valid within the secure world. Because the secure world typically holds sensitive cryptographic keys, authentication tokens, and other high-value assets, compromising its integrity poses a severe risk. The ability to trigger this condition locally means that any user account with access to execute tasks on the device can potentially destabilize the secure environment, leading to crashes or more sophisticated attacks where control over the processor state is gained through corrupted memory structures.
The operational impact of this vulnerability extends beyond simple denial of service. While a crash in the secure world might simply reset the device, the underlying use-after-free condition creates opportunities for privilege escalation and data exfiltration if an attacker can carefully craft inputs to exploit the dangling pointers. This aligns with CWE-416, Use After Free, which describes situations where memory is accessed after it has been freed, potentially allowing attackers to execute arbitrary code or bypass security controls. Furthermore, this flaw relates to ATT&CK technique T1059, Command and Scripting Interpreter, as the exploitation relies on invoking specific system calls (SVC) that act as entry points for executing privileged operations. The failure to enforce proper access control during these critical kernel-level transitions highlights a gap in CWE-269, Improper Privilege Management, where the principle of least privilege is not strictly enforced during context cleanup procedures.
To mitigate this risk and restore the integrity of the secure execution environment, it is imperative for users to upgrade FreeRTOS-Kernel to version 11.3.1 or any later release. The updated versions include patches that enforce strict privilege verification within the secure context cleanup handler, ensuring that only authorized entities can initiate deallocation processes in the secure world. This fix closes the attack vector by validating the caller's permissions before proceeding with memory management operations. Additionally, organizations should review their deployment configurations to ensure that unnecessary user accounts are disabled and that system call interfaces are restricted to trusted applications where possible. Regularly updating embedded systems running FreeRTOS is essential to maintain a robust security posture against such kernel-level vulnerabilities that can compromise both normal and secure execution domains.