CVE-2020-36203 in reffers Crate
Summary
by MITRE • 01/26/2021
An issue was discovered in the reffers crate through 2020-12-01 for Rust. ARefss can contain a !Send,!Sync object, leading to a data race and memory corruption.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 02/19/2021
The vulnerability identified as CVE-2020-36203 affects the reffers crate version 2020-12-01 and earlier in the Rust programming ecosystem. This issue represents a critical concurrency flaw that undermines the memory safety guarantees typically provided by Rust's ownership model. The reffers crate is designed to handle references and reference counting mechanisms, but the implementation contains a fundamental design flaw that permits the creation of potentially unsafe reference structures. The vulnerability specifically manifests when ARefss objects are constructed with Sync types, which are markers indicating that data cannot be safely transferred between threads or shared across concurrent contexts.
The technical root cause of this vulnerability lies in the improper handling of type constraints within the crate's reference management system. When a reference is created with Sync markers, the system should enforce strict single-threaded access patterns to prevent concurrent access. However, the reffers crate fails to properly validate or enforce these constraints, allowing potentially unsafe references to be created and subsequently used in multi-threaded contexts. This flaw directly relates to CWE-362, which describes a concurrency vulnerability involving a race condition that can occur when multiple threads access shared data without proper synchronization mechanisms. The absence of proper synchronization in this case creates a path for data races to occur, where multiple threads might simultaneously read and write to the same memory location, leading to unpredictable behavior and potential memory corruption.
The operational impact of this vulnerability is severe for any Rust application that relies on the reffers crate for reference management. Applications utilizing this crate in multi-threaded environments become susceptible to memory corruption vulnerabilities that could be exploited to cause system instability, data loss, or potentially more serious security implications. The vulnerability essentially undermines the memory safety guarantees that Rust developers rely on, creating a potential attack surface where malicious actors could manipulate concurrent access patterns to trigger undefined behavior. This type of flaw is particularly dangerous in systems where memory corruption could lead to privilege escalation or arbitrary code execution, as it represents a fundamental breach in the language's safety mechanisms. The vulnerability aligns with ATT&CK technique T1499.004, which involves network disruption through memory corruption, and could potentially be leveraged in broader attack chains targeting system stability and availability.
Mitigation strategies for this vulnerability require immediate attention from developers and system administrators. The primary recommendation is to upgrade to a patched version of the reffers crate that properly enforces type constraints and prevents the creation of unsafe reference structures. Organizations should conduct thorough code reviews to identify all instances where the affected crate is used, particularly in multi-threaded contexts where the risk of data races is highest. Additionally, developers should implement comprehensive testing procedures that include concurrent access scenarios to validate the safety of reference management code. The vulnerability demonstrates the importance of rigorous testing for concurrency-related issues, especially in systems where memory safety is paramount. Security teams should also consider implementing runtime monitoring to detect anomalous memory access patterns that could indicate exploitation attempts. Given the nature of the vulnerability, which involves fundamental concurrency flaws, developers should also re-evaluate their use of unsafe code patterns and ensure that all shared data structures properly implement appropriate synchronization mechanisms to prevent similar issues in other parts of their codebase.