CVE-2024-1023 in Vert.x
Summary
by MITRE • 03/27/2024
A vulnerability in the Eclipse Vert.x toolkit results in a memory leak due to using Netty FastThreadLocal data structures. Specifically, when the Vert.x HTTP client establishes connections to different hosts, triggering the memory leak. The leak can be accelerated with intimate runtime knowledge, allowing an attacker to exploit this vulnerability. For instance, a server accepting arbitrary internet addresses could serve as an attack vector by connecting to these addresses, thereby accelerating the memory leak.
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Analysis
by VulDB Data Team • 06/24/2025
The vulnerability identified as CVE-2024-1023 represents a critical memory management flaw within the Eclipse Vert.x toolkit that leverages Netty FastThreadLocal data structures to create persistent memory leaks. This issue manifests specifically when the Vert.x HTTP client establishes connections to multiple distinct hosts, creating a scenario where thread-local storage accumulates without proper cleanup. The underlying mechanism exploits the FastThreadLocal implementation within Netty, which is designed for high-performance thread-local storage but becomes problematic when not properly managed in long-running applications. The vulnerability stems from the improper lifecycle management of these thread-local variables, causing them to persist in memory even after their intended use has concluded, leading to progressive memory consumption that can ultimately result in application instability or complete system failure.
The technical exploitation of this vulnerability requires understanding the specific runtime conditions that trigger the memory leak pattern. Attackers can accelerate the memory consumption by leveraging intimate knowledge of the application's runtime behavior and connection patterns, particularly when the application serves as a proxy or gateway that accepts arbitrary internet addresses for connection. This creates a direct attack vector where malicious actors can systematically connect to various remote hosts, causing rapid accumulation of leaked memory through the FastThreadLocal mechanism. The vulnerability's impact is amplified when the application operates in high-throughput scenarios where numerous concurrent connections are established and maintained, as each connection attempt contributes to the accumulation of leaked thread-local storage. The leak occurs because the FastThreadLocal objects are not properly removed from the thread-local map when connections are closed or recycled, creating a memory retention issue that grows linearly with the number of connections processed.
The operational impact of CVE-2024-1023 extends beyond simple memory consumption issues to potentially destabilize entire application environments and affect system availability. Applications running vulnerable versions of Vert.x may experience progressive performance degradation as memory leaks accumulate, eventually leading to OutOfMemoryError exceptions and application crashes. The vulnerability is particularly dangerous in server-side applications that handle dynamic connection targets, such as reverse proxies, API gateways, or any service that routes traffic to arbitrary destinations. From a security perspective, this vulnerability aligns with CWE-401, which addresses improper release of memory, and can be mapped to ATT&CK technique T1499.200, specifically targeting resource exhaustion through memory consumption. The vulnerability's exploitation can lead to denial of service conditions where legitimate users experience service degradation or complete unavailability, making it a critical concern for enterprise applications and cloud services that rely on Vert.x for high-performance HTTP processing.
Mitigation strategies for CVE-2024-1023 require immediate attention through version upgrades to patched releases of the Eclipse Vert.x toolkit where the FastThreadLocal management has been corrected. Organizations should implement comprehensive monitoring of memory usage patterns in applications utilizing Vert.x to detect early signs of memory leak accumulation, particularly in services handling dynamic connection targets. The recommended approach includes deploying automated alerting systems that trigger when memory consumption exceeds predefined thresholds, allowing for proactive intervention before complete system failure occurs. Additionally, application architects should consider implementing connection pooling strategies and connection lifecycle management that explicitly clean up thread-local resources when connections are closed or recycled. Security teams should also evaluate their application's exposure to this vulnerability by analyzing connection patterns and identifying services that accept arbitrary host addresses, implementing rate limiting or connection validation mechanisms to reduce the attack surface. The fix typically involves proper cleanup of FastThreadLocal objects during connection termination and ensuring that thread-local storage is released appropriately when resources are no longer needed, addressing the root cause of the memory retention issue.