CVE-2018-25023 in smallvec Crate
Summary
by MITRE • 12/27/2021
An issue was discovered in the smallvec crate before 0.6.13 for Rust. It can create an uninitialized value of any type, including a reference type.
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Analysis
by VulDB Data Team • 03/09/2026
The vulnerability identified as CVE-2018-25023 represents a critical memory safety issue within the smallvec crate version 0.6.12 and earlier, affecting Rust programming environments. This flaw resides in the crate's handling of uninitialized memory allocation, specifically allowing the creation of uninitialized values of arbitrary types including reference types. The smallvec crate serves as a memory management utility that provides a vector-like data structure capable of storing a small number of elements inline within the vector structure itself, transitioning to heap allocation only when necessary. The vulnerability arises from insufficient validation during the initialization process of memory regions, particularly when the crate attempts to optimize memory usage by creating uninitialized storage areas.
The technical implementation of this vulnerability stems from the crate's internal memory management functions that do not properly enforce type safety when allocating uninitialized memory blocks. When the smallvec crate processes operations requiring memory allocation, it may inadvertently create uninitialized memory regions that contain garbage values or invalid references. The flaw becomes particularly dangerous when these uninitialized values are of reference types, as they can point to invalid memory locations or contain corrupted data that leads to undefined behavior. This issue is classified under CWE-457 as "Use of Uninitialized Variable" and specifically relates to improper handling of uninitialized memory in memory management libraries. The vulnerability demonstrates a fundamental failure in Rust's memory safety guarantees when interacting with third-party crates that do not properly implement safe memory initialization practices.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially enabling attackers to exploit the uninitialized memory to achieve arbitrary code execution or information disclosure. When applications using vulnerable versions of smallvec process data through the affected memory management functions, they may inadvertently expose uninitialized memory to external input or create conditions where malicious actors can manipulate the uninitialized references to gain unauthorized access. The risk is particularly elevated in applications that process untrusted input through memory-intensive data structures, as attackers could potentially craft inputs that trigger the vulnerable code paths. This vulnerability aligns with ATT&CK technique T1059.001 for "Command and Scripting Interpreter: PowerShell" and T1068 for "Exploitation for Privilege Escalation" when exploited in environments where memory corruption can be leveraged for privilege escalation. The flaw also contributes to broader memory safety issues within Rust applications, as it demonstrates how third-party libraries can undermine the language's inherent safety guarantees.
Mitigation strategies for this vulnerability require immediate upgrade to smallvec version 0.6.13 or later, which implements proper initialization of memory regions and prevents the creation of uninitialized values. System administrators and developers should conduct comprehensive code reviews to identify all dependencies using vulnerable versions of the smallvec crate, particularly in applications handling sensitive data or operating in security-critical environments. The fix involves ensuring that all memory allocation operations properly initialize allocated memory regions before making them available for use, preventing any possibility of uninitialized memory exposure. Organizations should implement automated dependency checking mechanisms to prevent introduction of vulnerable libraries into their software supply chains. Additionally, developers should consider implementing memory safety testing procedures that specifically target uninitialized memory scenarios and ensure that all third-party libraries undergo security validation before deployment. The vulnerability serves as a reminder of the importance of memory safety in Rust applications and the critical need for proper initialization practices even within well-designed memory management utilities.