A recently discovered vulnerability (CVE-2023-5685) in the XNIO library could potentially lead to uncontrolled resource management and Denial of Service (DoS) attacks. This critical flaw revolves around the improper handling of the XNIO NotifierState when the chain of notifier states becomes problematically large, causing a Stack Overflow Exception. In this post, we'll take a deep dive into understanding the vulnerability, its potential impact, exploitations, and mitigation strategies.

XNIO Library

XNIO is a low-level I/O layer library that simplifies many of the complexities of Java's I/O system. It provides a simple and straightforward API for creating and managing I/O channels, making the library popular for developers working on networked applications. However, as with any software, vulnerabilities can exist, and the recently discovered CVE-2023-5685 is a prime example.

The Vulnerability

The core of this vulnerability lies in the XNIO NotifierState. Under certain conditions, the chain of notifier states can become problematically large and cause a Stack Overflow Exception. This situation can escalate into uncontrolled resource management and potentially facilitate a DoS attack. When a system is flooded with requests, it will spend most of its resources processing those requests, leaving legitimate users unable to access the system.

Here's a snippet of the vulnerable code

public class NotifierState {
    private final NotifierState parent;
    private final Set<Object> notifiers;

    public NotifierState(NotifierState parent) {
        this.parent = parent;
        notifiers = new HashSet<Object>();
     * This function adds a new notifier into the chain.
    public void addNewNotifier(Object notifier) {
     * In this function, the issue occurs when the chain becomes too large
     * causing a Stack Overflow Exception.
    public boolean containsNotifier(Object notifier) {
        return notifiers.contains(notifier) || (parent != null && parent.containsNotifier(notifier));

Exploit Details

An attacker could exploit this vulnerability by sending a large number of requests with distinct notifier objects to the system. This action triggers the Stack Overflow Exception and exhausts the server's resources, denying service to legitimate users.

1. XNIO library: https://github.com/xnio/xnio
2. Vulnerability description: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-5685

Mitigation Strategies

The most straightforward way to mitigate this vulnerability would be to update the XNIO library with a patched version that resolves the issue. Another approach would be to implement a rate-limiting mechanism on the server to limit the number of requests a single client can send. This technique would not only prevent the Stack Overflow Exception from happening but also help protect the system against DoS attacks in general.


CVE-2023-5685 is a critical vulnerability in the XNIO library and has the potential to severely impact systems that rely on this library for I/O management. Developers and system administrators should take this issue seriously and implement the appropriate patch or mitigation strategies to safeguard their users and systems from potential DoS attacks.

Stay vigilant and keep your systems updated to protect against vulnerabilities.


Published on: 03/22/2024 19:15:07 UTC
Last modified on: 03/25/2024 01:51:01 UTC