CVE-2020-36472 in max7301 Crate
Summary
by MITRE • 08/08/2021
An issue was discovered in the max7301 crate before 0.2.0 for Rust. The ImmediateIO and TransactionalIO types implement Sync for all Expander types that they contain.
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Analysis
by VulDB Data Team • 08/14/2021
The vulnerability identified in CVE-2020-36472 affects the max7301 crate version 0.2.0 and earlier in the Rust programming language ecosystem. This issue resides within the hardware abstraction layer designed for controlling max7301 GPIO expanders, which are commonly used in embedded systems and IoT devices for extending GPIO capabilities. The crate provides two primary interfaces for interacting with these expanders: ImmediateIO and TransactionalIO types that are intended to offer different approaches to GPIO operations. The problem emerges from the implementation of synchronization traits for these types, creating a fundamental design flaw that can compromise system integrity and security in multi-threaded environments.
The technical flaw manifests in the improper implementation of the Sync trait for both ImmediateIO and TransactionalIO types within the max7301 crate. This design decision allows these types to be safely shared across thread boundaries without proper synchronization mechanisms, despite containing references to expander hardware that may not be inherently thread-safe. The Sync trait in Rust indicates that a type can be safely shared between threads, but this implementation incorrectly assumes that all expander types can be safely shared regardless of their underlying hardware characteristics or current operational state. This violates fundamental concurrency safety principles and creates potential race conditions when multiple threads attempt to access the same GPIO expander simultaneously through these interfaces.
The operational impact of this vulnerability extends beyond simple concurrency issues to potentially enable various security exploits and system instability. In embedded systems environments where the max7301 crate is commonly deployed, multiple threads may attempt to control the same GPIO expanders through different interface types, leading to unpredictable behavior and potential system crashes. The vulnerability becomes particularly dangerous in scenarios involving real-time systems or critical infrastructure where consistent GPIO behavior is essential. Attackers could potentially exploit this weakness to cause denial of service conditions, corrupt GPIO states, or manipulate hardware interactions in ways that compromise system security. The flaw also affects the crate's ability to provide reliable hardware abstraction, as developers cannot trust that concurrent access patterns will maintain consistent hardware states.
Mitigation strategies for CVE-2020-36472 require immediate attention from developers using the affected crate. The primary solution involves upgrading to version 0.2.0 or later where the synchronization implementation has been corrected to properly handle thread safety considerations. Developers should also review their code to ensure that any concurrent access patterns to GPIO expanders are properly synchronized using appropriate Rust concurrency primitives such as mutexes or other synchronization mechanisms when dealing with shared expander resources. The vulnerability aligns with CWE-362, which describes a race condition in concurrent programming, and could potentially map to ATT&CK technique T1059.001 for command and scripting interpreter execution in embedded systems contexts. Organizations should also implement proper code review processes to identify similar concurrency issues in other hardware abstraction crates and ensure that synchronization guarantees are properly enforced throughout their embedded software ecosystems.