CVE-2026-102757 in ThreadX
Summary
by MITRE • 09/29/2026
An unprivileged, memory-protected ThreadX module can have the kernel read and write memory at addresses of its choosing, in privileged mode, and can use that to clear the MPU enable bit and remove its own isolation boundary.
The Module Manager decided whether a privileged service could dereference an object address a module named by asking only whether that address fell outside the module. The manager's object pool is outside every module, so the test was satisfied by an address shifted into the interior of one of the module's own privileged allocations, which denotes no object at all. The bytes such an address presents as a control block are bytes the module put there through ordinary create and set services, so the control block ID at the front of them could be made to read as any type the module chose, and the `_txe_` layer's ID test then agreed. The reported chain uses that to reach a privileged `memset` across an attacker-chosen range.
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Analysis
by VulDB Data Team • 09/29/2026
The vulnerability described constitutes a critical privilege escalation flaw within the ThreadX real-time operating system kernel, specifically affecting modules protected by Memory Protection Unit (MPU) mechanisms. In this architecture, unprivileged user-mode threads are typically isolated from privileged kernel memory through hardware-enforced boundaries defined by the MPU. However, due to an insufficient validation logic in the Module Manager component, a malicious or compromised module can bypass these isolation barriers. The core issue lies in how the system validates object access permissions for privileged services invoked by modules. Instead of performing strict bounds checking against the specific allocation limits of the calling module, the manager relies on a flawed heuristic that checks whether an address falls outside the general scope of any known module's protected region. This logic fails to account for addresses that are shifted or manipulated to point into internal memory regions allocated to privileged services within the same module context but which do not correspond to valid kernel objects.
By exploiting this logical error, an attacker can craft a request where the target address is calculated to land in a gap between modules or inside a reserved area of their own allocation that happens to be outside the strict definition of any specific protected object pool yet remains within memory accessible by the module during privileged execution. When such an invalid address is passed to kernel services, it does not map to a legitimate control block. However, because the attacker controls the content of this memory region through standard create and set operations, they can populate these bytes with crafted data that mimics the structure of valid kernel control blocks. Specifically, by setting the initial identifier field to match expected types for internal ThreadX structures, the `txe` error handling layer accepts the request as legitimate due to its reliance on this ID check rather than a comprehensive structural validation or pointer integrity verification.
Once the kernel is tricked into treating arbitrary memory locations as valid control blocks, it proceeds with operations intended for those objects. In the reported exploitation chain, this mechanism allows an unprivileged module to invoke privileged functions that operate across attacker-chosen ranges of memory. The most severe consequence demonstrated is the ability to execute a `memset` operation in privileged mode over a range selected by the attacker. This capability effectively neutralizes the security model because it permits the modification of critical kernel data structures, including potentially clearing or altering bits within hardware registers such as those controlling MPU settings. By manipulating these memory regions, an attacker can disable the MPU enable bit, thereby removing all isolation boundaries and granting full read-write access to the entire system memory space from user mode.
This vulnerability aligns with CWE-20 Improper Input Validation, specifically regarding insufficient checking of object references or pointers before use in privileged operations. It also relates closely to CWE-787 Out-of-bounds Write when considering the potential for writing beyond intended limits if the range calculation is manipulated further. From a threat modeling perspective using MITRE ATT&CK, this behavior maps to T1068 Exploitation for Privilege Escalation and potentially T1499 Endpoint Denial of Service if the memory corruption leads to system instability or crashes. The exploitation path demonstrates how logical flaws in access control mechanisms can undermine hardware-enforced security features like MPU isolation.
Mitigation strategies must focus on hardening the validation logic within the Module Manager and kernel object dereferencing routines. Developers should implement strict bounds checking that verifies not only whether an address is outside protected modules but also ensures it points to a valid, allocated object of the expected type with correct structural integrity checks beyond simple ID matching. Additionally, enforcing stricter separation between user-mode accessible memory and privileged kernel data structures can prevent attackers from placing crafted control block headers in locations that are misinterpreted as valid targets. Updating to patched versions of ThreadX where these validation routines have been corrected is essential for maintaining system security posture against such privilege escalation attacks.