CVE-2018-20996 in crossbeam Crate
Summary
by MITRE
An issue was discovered in the crossbeam crate before 0.4.1 for Rust. There is a double free because of destructor mishandling.
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Analysis
by VulDB Data Team • 12/04/2023
The vulnerability identified as CVE-2018-20996 affects the crossbeam crate version 0.4.0 and earlier in the Rust programming language ecosystem. This issue represents a critical memory safety flaw that manifests through improper destructor handling mechanisms within the crate's implementation. The crossbeam crate serves as a foundational library for concurrent programming in rust applications, providing various synchronization primitives and data structures that enable safe multi-threaded operations. When developers integrate this crate into their projects, they unknowingly introduce a potential pathway for memory corruption vulnerabilities that could be exploited by malicious actors.
The technical root cause of this vulnerability stems from a double free condition occurring during object destruction sequences. In memory management, a double free occurs when the same memory location is deallocated twice, leading to undefined behavior and potential security exploits. The crossbeam crate's destructor implementation fails to properly track object lifetimes and memory allocation states, causing the system to attempt freeing the same memory block multiple times. This flaw specifically affects the crate's handling of certain data structures and synchronization primitives that rely on complex memory management patterns. The improper destructor logic creates scenarios where objects are dropped and freed in sequences that result in overlapping memory deallocations, fundamentally compromising the memory integrity of applications using this library.
The operational impact of CVE-2018-20996 extends beyond simple memory corruption, potentially enabling arbitrary code execution and system compromise. Attackers could exploit this vulnerability by crafting specific inputs or operations that trigger the problematic destructor paths within the crossbeam crate. The vulnerability affects any rust application that depends on the affected version of crossbeam, particularly those implementing concurrent programming patterns or utilizing synchronization primitives. Given the widespread adoption of crossbeam in the rust ecosystem, this vulnerability represents a significant threat vector across numerous applications and systems. The double free condition creates opportunities for heap-based exploits, potentially allowing attackers to manipulate memory layout, overwrite critical data structures, or even execute malicious code within the context of the vulnerable application.
Mitigation strategies for CVE-2018-20996 focus primarily on updating to the patched version of the crossbeam crate. Version 0.4.1 and later releases contain the necessary fixes to address the destructor mishandling issues and eliminate the double free conditions. System administrators and developers should prioritize updating their dependencies to ensure compliance with security best practices. The vulnerability aligns with CWE-415, which specifically addresses double free conditions in memory management, and represents a classic example of improper resource management in concurrent programming contexts. Organizations should implement comprehensive dependency auditing processes to identify all systems utilizing vulnerable versions of crossbeam and other similar crates. Additionally, developers should consider implementing memory safety testing procedures and static analysis tools to detect similar patterns in their own codebases, as this vulnerability demonstrates the importance of careful destructor implementation in concurrent programming environments. The remediation process requires thorough testing of updated applications to ensure compatibility and prevent regression issues while maintaining the security posture against this specific memory corruption vulnerability.