CVE-2026-94192 in ThreadX
Summary
by MITRE • 10/20/2026
A ThreadX module allocates the control blocks of its kernel objects from the Module Manager's object pool, and can ask for that memory back by address with `txm_module_object_deallocate`. The manager released it whatever was in it, including a control block the kernel was still using. Deallocation is not deletion: the object stays on the created list for its type, a thread stays wherever it was on the ready or suspension lists and stays schedulable, and an active timer stays on the timer list. The byte pool is meanwhile free to hand those same bytes to the next allocation.
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Analysis
by VulDB Data Team • 10/20/2026
The vulnerability described involves a critical memory management flaw within the ThreadX real-time operating system kernel, specifically concerning the interaction between module-level object control blocks and the underlying Module Manager's object pool. This issue stems from an improper handling of resource deallocation where the system fails to maintain consistency between logical state tracking and physical memory availability. When a specific ThreadX module requests the return of its allocated kernel object control blocks via the txm_module_object_deallocate function, the manager releases these memory regions back into the general pool without ensuring that all references to those objects are invalidated or removed from active scheduling structures. This creates a scenario where the operating system retains logical pointers to resources that have been physically freed and marked as available for reuse by other processes or modules.
The core technical flaw lies in the decoupling of object lifecycle management from memory pool management. In a properly secured real-time kernel, deallocating an object should involve removing it from all relevant data structures such as ready lists, suspension queues, and timer chains before returning its memory to the heap. However, in this vulnerable implementation, while the byte pool is free to hand those same bytes to the next allocation request, the control blocks remain on their respective created lists for their specific types. Threads associated with these objects stay wherever they were positioned on ready or suspension lists and remain schedulable by the kernel scheduler. Similarly, active timers continue to reside on the timer list despite having been logically deallocated at the module level. This discrepancy means that the kernel's internal state no longer accurately reflects the actual availability of memory resources, leading to a classic use-after-free condition where previously freed memory is accessed as if it were still valid and owned by the original context.
The operational impact of this vulnerability is severe due to its potential for arbitrary code execution or system instability. Because the byte pool can immediately reallocate these same memory addresses to new objects, any subsequent allocation might overwrite data within a control block that the kernel believes is still in use but has been logically deallocated. If an attacker or malicious module can influence which object gets allocated into those recycled memory regions, they may be able to manipulate critical kernel structures such as thread stacks, timer callbacks, or synchronization primitives. This could lead to privilege escalation if lower-privileged modules gain control over higher-level kernel operations through corrupted data in reused control blocks. Furthermore, the persistence of threads on ready lists means that stale execution contexts might resume running with corrupted stack frames or invalid pointers, resulting in unpredictable behavior, system crashes, or denial of service conditions where the real-time guarantees provided by ThreadX are completely compromised.
From a classification perspective, this vulnerability aligns closely with CWE-416 Use After Free, as it involves accessing memory after it has been freed without proper validation of its current ownership status. It also relates to CWE-362 Concurrent Execution Using Shared Resource with Improper Synchronization because the race condition between deallocation and continued access by kernel scheduling mechanisms creates an unsafe state. In terms of MITRE ATT&CK, this flaw could be exploited via techniques associated with Defense Evasion or Privilege Escalation, particularly if an attacker leverages the corrupted control blocks to bypass security checks or inject malicious code into active threads. The lack of synchronization between module-level deallocation requests and kernel-level object removal mechanisms represents a fundamental design weakness in resource lifecycle management within embedded real-time environments.
Mitigation strategies must focus on enforcing strict consistency between logical state transitions and physical memory reclamation. Developers should modify the txm_module_object_deallocate implementation to ensure that before any control block is returned to the byte pool, it is completely removed from all active kernel lists including ready queues, suspension chains, and timer wheels. Additionally, implementing pointer invalidation or tagging mechanisms can help detect stale references during runtime debugging phases. It is crucial to audit all module-level interactions with kernel objects to ensure that deallocation requests trigger comprehensive cleanup routines rather than simple memory release operations. Regular static analysis and dynamic testing using fuzzing tools targeted at real-time operating system APIs can further identify similar inconsistencies in other parts of the codebase, ensuring robustness against both accidental corruption and intentional exploitation attempts in safety-critical embedded systems.