CVE-2020-36204 in im Crate
Summary
by MITRE • 01/26/2021
An issue was discovered in the im crate through 2020-11-09 for Rust. Because TreeFocus does not have bounds on its Send trait or Sync trait, a data race can occur.
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Analysis
by VulDB Data Team • 02/19/2021
The vulnerability identified as CVE-2020-36204 resides within the im crate version 2020-11-09 and earlier, representing a critical concurrency flaw that undermines memory safety guarantees in Rust applications. This issue specifically targets the TreeFocus type within the crate, where the absence of proper bounds on the Send and Sync traits creates an exploitable condition that allows for data races during concurrent execution. The im crate serves as an immutable data structure library for Rust, providing efficient functional programming constructs that are widely utilized in systems requiring thread-safe data manipulation. When developers use TreeFocus in concurrent contexts without proper synchronization, the lack of Send and Sync bounds creates a dangerous scenario where multiple threads can simultaneously access and modify shared data structures, leading to undefined behavior and potential system instability.
The technical root cause of this vulnerability stems from the improper implementation of Rust's trait system within the TreeFocus type. In Rust, the Send and Sync traits are fundamental to memory safety, with Send indicating that a type can be safely transferred between threads and Sync indicating that a type can be safely shared between threads. The absence of these bounds in TreeFocus means that the compiler cannot enforce safety guarantees when the type is used in concurrent contexts. This flaw directly violates the principles outlined in CWE-362, which describes concurrent execution using shared data without proper synchronization mechanisms. The vulnerability enables a classic data race condition where multiple threads can simultaneously read and write to the same memory location, creating unpredictable behavior that can lead to memory corruption, application crashes, or potentially exploitable conditions.
The operational impact of CVE-2020-36204 extends beyond simple performance degradation to potentially compromising the integrity and availability of applications that rely on the im crate for concurrent data handling. When applications using this crate are deployed in multi-threaded environments, the vulnerability can manifest as intermittent crashes, data corruption, or inconsistent program behavior that is extremely difficult to debug and reproduce. Attackers could potentially exploit this condition to perform memory corruption attacks or create denial of service scenarios by carefully orchestrating concurrent access patterns. The vulnerability also impacts the broader Rust ecosystem, as many applications and libraries depend on the im crate for their data structure needs, making this a widespread concern that affects numerous software projects. According to ATT&CK framework concept T1499.004, this vulnerability could be leveraged to disrupt services through memory corruption or system instability.
Mitigation strategies for CVE-2020-36204 require immediate action from developers and system administrators to address the root cause of the concurrency issue. The most effective immediate solution involves upgrading to a patched version of the im crate where proper Send and Sync bounds have been implemented to prevent unsafe concurrent access patterns. Developers should also conduct thorough code reviews to identify all usages of TreeFocus and other potentially affected types within their applications, ensuring that proper synchronization mechanisms such as mutexes or channels are implemented when concurrent access is required. Additionally, organizations should implement comprehensive testing procedures including race condition detection tools like thread sanitizers or formal verification methods to identify similar issues in other parts of their codebase. The vulnerability highlights the importance of adhering to Rust's safety principles and demonstrates how seemingly minor trait implementations can have significant security implications, particularly in concurrent programming contexts where proper synchronization is paramount for maintaining system integrity and preventing exploitation.