CVE-2020-35893 in simple-slab Crate
Summary
by MITRE • 12/31/2020
An issue was discovered in the simple-slab crate before 0.3.3 for Rust. remove() has an off-by-one error, causing memory leakage and a drop of uninitialized memory.
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Analysis
by VulDB Data Team • 12/31/2020
The vulnerability in the simple-slab crate prior to version 0.3.3 represents a critical memory safety issue that fundamentally compromises the integrity of memory management operations within Rust applications. This flaw manifests in the remove() function where an off-by-one error occurs, creating a condition where one element beyond the intended removal boundary is incorrectly processed. The issue stems from improper boundary calculations during array or slice manipulation, which directly violates fundamental memory safety principles that Rust is designed to enforce.
The technical implementation of this vulnerability allows for two distinct but related memory safety failures that can lead to unpredictable application behavior and potential exploitation. When the remove() function executes, the off-by-one error causes the system to attempt to drop memory that was never properly initialized, leading to undefined behavior as uninitialized memory contains arbitrary data that could include sensitive information or corrupted values. Additionally, this error creates memory leakage conditions where allocated memory blocks are not properly deallocated, resulting in gradual memory consumption that can eventually lead to application instability or resource exhaustion.
The operational impact of this vulnerability extends beyond simple memory management issues and can create cascading failures within applications that rely on the simple-slab crate for efficient memory allocation and deallocation. Attackers could potentially exploit the uninitialized memory drop scenario to extract sensitive information from memory locations or manipulate application state through controlled data corruption. The memory leakage aspect creates persistent resource consumption that can degrade system performance over time, making this vulnerability particularly dangerous in long-running applications or systems with limited memory resources. This type of vulnerability directly maps to CWE-129 and CWE-416 within the Common Weakness Enumeration framework, representing both improper boundary checking and use after free conditions.
Mitigation strategies for this vulnerability require immediate upgrading to version 0.3.3 or later of the simple-slab crate, as this release contains the necessary fixes to correct the boundary calculation logic in the remove() function. Organizations should also implement comprehensive code review processes to identify similar off-by-one errors in their own codebases, particularly in memory management routines that handle dynamic arrays or slices. The remediation process should include thorough testing of memory allocation patterns and verification that all memory operations properly handle boundary conditions. Additionally, security teams should monitor for similar patterns in other third-party crates and consider implementing automated scanning tools to detect potential memory safety issues within their dependency trees. This vulnerability demonstrates the importance of rigorous testing for memory safety in systems that utilize Rust's memory management features, and aligns with ATT&CK technique T1068 which involves privilege escalation through memory corruption vulnerabilities.