CVE-2026-102711 in ThreadX
Summary
by MITRE • 09/29/2026
Two issues in the ThreadX loadable-module loader, reached when a device loads an attacker-controlled module object via `_txm_module_manager_memory_load` / `_txm_module_manager_in_place_load` — APIs that take ONLY a base pointer, no image length, so every size/offset field in `TXM_MODULE_PREAMBLE` is fully attacker-trusted: (1) a heap OOB **read** (`code_size` trusted as the source-image length in the code-copy loop), and (2) a control-flow-integrity / defense-in-depth gap (module entry/start/callback/stop pointers computed as `code_start + preamble_offset` with only a `!= 0` check, and the preamble `checksum` never verified). No controlled OOB write was found (honest — the copy destination is overflow-guarded).
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/29/2026
The vulnerability resides within the ThreadX loadable-module loader subsystem, specifically affecting the APIs _txm_module_manager_memory_load and _txm_module_manager_in_place_load. These functions are designed to handle dynamic module loading on embedded devices but suffer from a fundamental architectural flaw regarding input validation. The core issue is that these APIs accept only a base pointer for the module image without requiring an explicit length parameter. Consequently, every size and offset field contained within the TXM_MODULE_PREAMBLE structure is treated as fully trusted data provided by the attacker who supplies the malicious module object. This design choice removes any boundary checks against external input, creating a severe trust assumption that leads to multiple critical security failures including out-of-bounds memory access and broken control flow integrity mechanisms.
The first major technical flaw is an out-of-bounds read vulnerability classified under CWE-125. During the execution of the code-copy loop, the loader utilizes the code_size field from the untrusted preamble as the definitive source-image length. Because this value is not validated against actual available memory or image boundaries, an attacker can craft a module with an artificially inflated code_size value. This causes the copy operation to read beyond the allocated buffer limits into adjacent memory regions. While no controlled out-of-bounds write was identified because the destination overflow is guarded by other mechanisms, the uncontrolled read still poses significant risks. It allows for potential information disclosure where sensitive data residing in neighboring memory spaces can be leaked through side channels or subsequent processing of corrupted state. This aligns with CWE-20 which covers improper input validation leading to security vulnerabilities via out-of-bounds reads.
The second critical issue involves a failure in control-flow integrity and defense-in-depth principles, mapping closely to CWE-841 Improper Enforcement of Behavioral Workflow and potentially CWE-94 Improper Control of Generation of Code. The loader computes pointers for module entry points, start routines, callbacks, and stop handlers by adding the preamble_offset to the code_start address. Crucially, these computed addresses are only subjected to a basic non-zero check rather than rigorous validation against valid executable memory regions or function boundaries. Furthermore, the checksum field within the preamble is never verified during the loading process. This absence of integrity verification means that an attacker can manipulate these pointers to redirect execution flow arbitrarily. If the calculated address points to writable memory or contains shellcode injected via the earlier out-of-bounds read side effects, it may facilitate arbitrary code execution. The lack of checksum validation further exacerbates this by allowing tampered module headers to be accepted without detection, bypassing standard integrity checks expected in secure embedded systems.
From an operational perspective, these vulnerabilities compromise the isolation guarantees provided by ThreadX modules. An attacker who can influence or supply a loadable module object gains the ability to read arbitrary memory contents and potentially hijack control flow within the host application context. In resource-constrained environments typical of IoT devices running ThreadX, such flaws can lead to complete system compromise, denial of service through crashes caused by invalid pointer dereferences, or persistent backdoors if execution is redirected to malicious payloads. The combination of untrusted size fields and unchecked function pointers creates a potent attack surface that undermines the security model of dynamic module loading entirely.
Mitigation strategies must address both the architectural design flaws and specific implementation gaps. First, the API interface should be modified to require an explicit image length parameter from the caller rather than relying on values embedded within the untrusted preamble data. This ensures that size fields are validated against actual buffer boundaries before any copy operations occur. Second, strict validation of all function pointers must be implemented. Instead of a simple non-zero check, loaders should verify that computed addresses fall within known executable memory regions and adhere to alignment requirements. Third, cryptographic verification or integrity checksums for the preamble and module content must be enforced prior to loading. Finally, adopting defense-in-depth measures such as enabling hardware-based execution protection (NX bit) can mitigate exploitation of control-flow hijacking attempts even if validation fails entirely. These changes align with best practices outlined in CWE-20 for input validation and ATT&CK techniques related to process injection or dynamic library linking where trust boundaries are improperly enforced.