CVE-2020-36213 in abi_stable Crate
Summary
by MITRE • 01/26/2021
An issue was discovered in the abi_stable crate before 0.9.1 for Rust. A retain call can create an invalid UTF-8 string, violating soundness.
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Analysis
by VulDB Data Team • 02/20/2021
The vulnerability identified as CVE-2020-36213 resides within the abi_stable crate version 0.9.1 and earlier, representing a critical soundness issue that fundamentally compromises the memory safety guarantees inherent to rust programming. This flaw manifests through the retain method implementation which, when invoked on strings, can produce invalid UTF-8 sequences that violate the fundamental assumptions of Rust's type system and memory safety model. The abi_stable crate serves as a library for creating stable application binary interfaces in rust, making it a critical component for developers who require binary compatibility across different versions of their software.
The technical root cause of this vulnerability stems from improper handling of string retention operations within the crate's implementation. When developers use the retain method to filter characters from strings, the underlying code fails to maintain proper UTF-8 encoding validity throughout the transformation process. This creates a scenario where strings that should remain valid UTF-8 can become corrupted, leading to undefined behavior when the application attempts to process these malformed strings. The flaw operates at a fundamental level of Rust's string handling mechanisms, specifically targeting the contract that strings must remain valid UTF-8 sequences at all times, a principle that is central to Rust's safety guarantees and forms part of the broader CWE-248 weakness category related to unspecified behavior in programming languages.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can enable attackers to exploit the soundness violation for more sophisticated attacks within the rust ecosystem. When applications using affected versions of abi_stable process user input or external data through retained string operations, they become susceptible to unexpected behavior that could potentially lead to information disclosure, denial of service, or even arbitrary code execution in certain contexts. The vulnerability particularly affects systems where binary compatibility is crucial and where developers rely on the abi_stable crate for creating stable interfaces between different software components. This risk is compounded by the fact that such soundness violations are often difficult to detect during normal testing procedures and can manifest only under specific conditions or with particular input patterns.
Mitigation strategies for CVE-2020-36213 require immediate action to upgrade to version 0.9.1 or later of the abi_stable crate, which contains the necessary fixes to ensure proper UTF-8 validation during string retention operations. Organizations should conduct comprehensive code reviews to identify all dependencies on vulnerable versions of the crate and ensure that their build processes consistently pull the patched versions. Additionally, developers should implement defensive programming practices such as validating string operations and ensuring that any retained strings are properly checked for UTF-8 validity before being processed further. The fix addresses the underlying issue by enforcing proper UTF-8 validation during retain operations, preventing the generation of invalid sequences that could compromise the safety guarantees of rust applications. This vulnerability aligns with ATT&CK technique T1059.008 for scripting languages and T1133 for external remote services, as it could enable attackers to exploit the soundness violation for remote code execution or privilege escalation within affected systems.