CVE-2020-36215 in hashconsing Crate
Summary
by MITRE • 01/26/2021
An issue was discovered in the hashconsing crate before 1.1.0 for Rust. Because HConsed does not have bounds on its Send trait or Sync trait, memory corruption can occur.
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Analysis
by VulDB Data Team • 02/20/2021
The vulnerability identified as CVE-2020-36215 resides within the hashconsing crate version 1.1.0 and earlier for the rust programming language. This issue stems from insufficient trait bounds in the HConsed type implementation, specifically lacking proper constraints on the Send and Sync traits. The hashconsing crate is designed to provide efficient storage and retrieval of hash-consed values, which are commonly used in compiler construction and symbolic computation systems where memory efficiency and value equality are paramount. When developers utilize this crate in concurrent environments, the absence of proper trait bounds creates a dangerous scenario that can lead to memory corruption.
The technical flaw manifests through the improper implementation of the Send and Sync traits for the HConsed type. In rust, these traits determine whether a type can be safely transferred between threads or shared across threads respectively. Without proper bounds, the compiler cannot guarantee that HConsed instances can be safely sent between threads or shared in concurrent contexts. This lack of type safety allows for potential race conditions and memory unsafety scenarios where multiple threads might simultaneously access or modify the same hash-consed data structure. The vulnerability becomes particularly dangerous in multi-threaded applications where the hashconsing crate is used to manage shared data structures, as it can lead to undefined behavior including memory corruption, data races, and potential exploitation of memory safety violations.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially enable more severe security consequences. In systems where hashconsing is used for managing compiler intermediate representations, symbolic execution engines, or any concurrent data structure that relies on hash-consed values, an attacker could potentially exploit this weakness to cause application crashes, data corruption, or even execute arbitrary code. The vulnerability affects any rust application that uses the hashconsing crate in concurrent scenarios, making it particularly concerning for systems that require high reliability and security such as compilers, interpreters, or distributed systems. The memory corruption that results from this flaw can manifest as heap corruption, use-after-free conditions, or other undefined behaviors that are notoriously difficult to debug and predict.
Mitigation strategies for CVE-2020-36215 involve updating to version 1.1.0 or later of the hashconsing crate where proper trait bounds have been implemented to ensure safe concurrent usage. Developers should also review their codebase to ensure that any usage of the hashconsing crate in concurrent contexts properly handles the Send and Sync bounds. The fix addresses the underlying CWE-472 Unprotected External Resource in the context of memory safety by ensuring proper trait bounds are enforced. This vulnerability aligns with ATT&CK technique T1059.001 Command and Scripting Interpreter: PowerShell where memory corruption vulnerabilities can be exploited to execute malicious code through compromised memory management. System administrators and developers should also implement static analysis tools that can detect improper trait usage and ensure that all dependencies are updated to their secure versions. The fix demonstrates the importance of proper trait bounds in rust systems and the necessity of following secure coding practices that prevent unsafe concurrent access patterns.