CVE-2018-21028 in Boa
Summary
by MITRE
Boa through 0.94.14rc21 allows remote attackers to trigger a memory leak because of missing calls to the free function.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 01/08/2024
The vulnerability identified as CVE-2018-21028 affects the Boa web server version 0.94.14rc21 and earlier, representing a critical memory management flaw that exposes the system to potential denial of service attacks. This issue stems from improper memory handling within the web server's codebase where specific memory allocations occur without corresponding deallocations, creating persistent memory leaks that can accumulate over time and ultimately exhaust available system resources. The vulnerability specifically manifests when the web server processes certain HTTP requests that trigger memory allocation patterns without proper cleanup mechanisms, allowing attackers to exploit this weakness remotely.
The technical root cause of this vulnerability aligns with CWE-401, which describes improper handling of memory allocation and deallocation in software systems. In the context of Boa web server, developers failed to implement proper memory cleanup routines for specific request processing paths, resulting in allocated memory blocks that remain unreleased even after their intended use has concluded. This memory leak pattern can be triggered through various HTTP methods and request structures that cause the server to allocate memory for processing but neglect to free it subsequently, creating a gradual degradation of system performance that can eventually lead to complete service unavailability.
From an operational impact perspective, this vulnerability enables remote attackers to systematically consume system memory resources without requiring authentication or specialized privileges. The memory leak occurs incrementally with each affected request, making it particularly dangerous in high-traffic environments where the accumulation of leaked memory can quickly overwhelm system resources. Attackers can maintain persistent resource exhaustion by repeatedly sending malicious requests that trigger the memory allocation paths, effectively creating a denial of service condition that can render the web server non-responsive to legitimate requests. This vulnerability also represents a significant concern for systems hosting sensitive web applications where availability is critical for business operations.
The exploitation of CVE-2018-21028 aligns with ATT&CK technique T1499.004, which involves resource exhaustion attacks targeting memory resources. The vulnerability can be leveraged as part of broader attack campaigns where attackers first establish persistent access to systems and then deploy memory exhaustion techniques to maintain control while degrading system performance. Security professionals should consider this vulnerability when assessing web server configurations and implementing defensive measures, particularly in environments where resource monitoring and automated alerting systems are crucial for detecting anomalous memory consumption patterns. The vulnerability also demonstrates the importance of proper code review processes and memory management practices in web server development, as highlighted in industry best practices for secure coding standards.
Mitigation strategies for this vulnerability include immediate deployment of patched versions of the Boa web server software, which should contain proper memory deallocation routines for all allocated memory blocks. System administrators should implement monitoring solutions that track memory usage patterns and alert on unusual consumption trends that may indicate exploitation attempts. Additionally, network-level controls such as rate limiting and connection throttling can help reduce the impact of exploitation attempts by limiting the number of requests that can be processed within specific time intervals. The vulnerability also underscores the necessity of regular security assessments and code audits to identify similar memory management issues in other components of the web infrastructure stack.