CVE-2026-95109 in ThreadX
Summary
by MITRE • 10/20/2026
The Cortex-A7 MMU Modules port validates a caller-supplied buffer by translating **one address** — the first byte. The common Module Manager hands its range check the module instance, the start address and the complete byte size; the Cortex-A7 implementation discarded the instance and the size and asked the MMU a single question about the start.
A memory-protected module therefore passed any range whose first byte was user-readable, however far the rest of it reached. Privileged dispatch code then read or wrote the whole range. Because every protected-module dispatcher that consumes a buffer or an extra-parameter array goes through this one macro, the defect is not in any individual service: it is in the primitive all of them rely on.
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Analysis
by VulDB Data Team • 10/20/2026
The vulnerability described constitutes a critical boundary condition error within the Cortex-A7 Memory Management Unit (MMU) module implementation, specifically affecting how memory access permissions are validated for user-supplied buffers. In secure system architectures, particularly those utilizing protected modules or sandboxed environments, it is imperative that any buffer provided by an untrusted caller be fully verified against the current privilege level and security policy before being accessed by privileged code. The flaw arises because the validation logic only checks the accessibility of the first byte in the supplied address range rather than validating the entire contiguous block of memory specified by the size parameter. This represents a fundamental failure to enforce complete boundary constraints, allowing an attacker to exploit this discrepancy by providing a buffer that starts at a readable location but extends into protected or inaccessible memory regions.
From a technical perspective, the defect lies in the interaction between the common Module Manager and the Cortex-A7 specific MMU implementation. The Module Manager correctly passes three parameters for validation: the module instance identifier, the starting virtual address, and the total byte size of the buffer. However, the Cortex-A7 port incorrectly discards both the module instance context and the size parameter during its internal check. Instead of iterating through or mapping the entire range to verify page-level permissions across all affected memory pages, it queries the MMU for a single translation status regarding only the initial address byte. Consequently, if the first byte resides in user-readable space, the validation routine returns success regardless of whether subsequent bytes fall into kernel-only, reserved, or unmapped regions where access would normally trigger a fault or exception.
The operational impact of this vulnerability is severe due to its pervasive nature within the affected software architecture. Because every protected-module dispatcher that consumes external buffers or extra-parameter arrays relies on this specific primitive for validation, the flaw affects all services utilizing this mechanism rather than being isolated to a single function. An attacker can leverage this by crafting malicious inputs where the initial address points to accessible memory but the length parameter is set large enough to encompass sensitive kernel data structures, control flow metadata, or other protected resources. When privileged dispatch code subsequently reads from or writes to this range based on the false assurance of validity, it may lead to arbitrary read/write operations outside the intended sandbox boundaries. This can result in information disclosure, privilege escalation, denial of service through system crashes caused by accessing invalid memory pages, or complete compromise of the host environment's integrity.
This vulnerability aligns with CWE-126 Buffer Over-read and CWE-399 Resource Leak without Proper Cleanup if the over-read leads to state corruption, but most accurately maps to CWE-787 Out-of-bounds Write when writes occur into protected memory or CWE-788 Access of Memory Location After End of Allowed Bounds. In terms of attack vectors, this behavior facilitates exploitation techniques associated with ATT&CK T1059 Command and Scripting Interpreter if the over-read allows injection of malicious payloads via corrupted parameters, or more directly relates to privilege escalation tactics where boundary checks are bypassed to access restricted resources. The lack of range validation is a classic example of insufficient input verification that undermines the security model's assumptions about memory isolation.
Mitigation strategies must focus on correcting the MMU module implementation to enforce strict bounds checking for all provided ranges. The Cortex-A7 port should be updated to utilize the size parameter passed by the Module Manager, ensuring that every page within the specified address range is individually validated against current access permissions before any privileged operation proceeds. Additionally, implementing runtime checks such as guard pages or using hardware-assisted boundary detection features available in modern MMUs can provide defense-in-depth layers. Developers should also consider adopting static analysis tools capable of detecting out-of-bounds memory accesses and enforcing coding standards that mandate explicit validation of both start addresses and lengths for all buffer operations involving untrusted inputs to prevent similar logical errors in future code revisions.