CVE-2019-12083 in Rust Programming Language Standard Library
Summary
by MITRE
The Rust Programming Language Standard Library 1.34.x before 1.34.2 contains a stabilized method which, if overridden, can violate Rust's safety guarantees and cause memory unsafety. If the `Error::type_id` method is overridden then any type can be safely cast to any other type, causing memory safety vulnerabilities in safe code (e.g., out-of-bounds write or read). Code that does not manually implement Error::type_id is unaffected.
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Analysis
by VulDB Data Team • 09/17/2023
The vulnerability identified as CVE-2019-12083 represents a critical memory safety issue within the Rust programming language standard library version 1.34.x prior to 1.34.2. This flaw exists in the stabilized method that governs error handling mechanisms within Rust's type system, specifically affecting the Error::type_id method which is part of the standard library's error trait implementation. The vulnerability stems from a fundamental design oversight that allows for unsafe type casting operations through method overriding, creating a pathway for memory unsafety that bypasses Rust's core safety guarantees. The issue manifests when developers override the Error::type_id method, which then enables arbitrary type casting between different types within the language's type system.
The technical nature of this vulnerability resides in how Rust's type system handles trait implementations and method overriding within the standard library's error handling framework. When the Error::type_id method is overridden, it creates a condition where the runtime type information can be manipulated to allow seemingly safe code to perform unsafe operations. This violation occurs because the method's implementation allows for type coercion that should normally be prevented by Rust's ownership and borrowing rules. The flaw essentially creates a backdoor that enables what would normally be compile-time safety checks to be bypassed at runtime, leading to potential memory corruption scenarios. According to CWE-471, this vulnerability maps to the category of "Modification of Assumed-Immutable Data" where the expected behavior of standard library methods is altered through improper override mechanisms.
The operational impact of this vulnerability extends beyond simple memory corruption to encompass broader security implications for applications written in Rust. Safe code that relies on Rust's memory safety guarantees becomes potentially compromised when the Error::type_id method is overridden, allowing attackers to perform out-of-bounds memory operations such as writes or reads that would normally be prevented. This creates a particularly dangerous scenario because the vulnerability operates at the language level rather than at the application level, meaning that even well-intentioned developers who follow security best practices could inadvertently expose their applications to memory safety violations. The exploitability of this vulnerability is enhanced by the fact that it can be triggered through legitimate method overriding patterns that developers might use for error handling customization, making detection and prevention particularly challenging.
Mitigation strategies for CVE-2019-12083 require immediate patching of affected Rust installations to version 1.34.2 or later, which addresses the core issue by ensuring that the Error::type_id method cannot be overridden in a manner that compromises memory safety. Organizations should conduct thorough code reviews to identify any custom implementations of the Error trait that might inadvertently override the type_id method, particularly in libraries or frameworks that extend Rust's standard error handling capabilities. System administrators should prioritize updating all development environments and production systems that utilize Rust versions prior to 1.34.2 to prevent exploitation. The vulnerability aligns with ATT&CK technique T1059.001 for the use of scripting languages and T1068 for the exploitation of privilege escalation mechanisms, as it creates conditions that could enable more sophisticated attacks through memory corruption. Additionally, developers should avoid custom implementations of the Error trait that modify type identification methods and instead rely on the standard library's safe implementations to maintain memory safety guarantees.