CVE-2026-45290: Cloudburst Network DoS Vulnerability

CVE-2026-45290 Overview

Cloudburst Network is a library that provides network components used within Cloudburst projects, including Minecraft server implementations built on Netty. A vulnerability in versions prior to 1.0.0.CR3-20260417.085727-30 allows a remote unauthenticated attacker to stall the Netty event loop, rendering the affected service inoperable. The flaw affects publicly accessible software that depends on the vulnerable Network library. The issue is tracked as CWE-770: Allocation of Resources Without Limits or Throttling and results in a denial of service condition against any exposed listener.

Critical Impact
Remote unauthenticated attackers can stall the Netty event loop and render dependent Cloudburst Network services inoperable without requiring credentials or user interaction.

Affected Products

Cloudburst Network library versions prior to 1.0.0.CR3-20260417.085727-30
Cloudburst projects that depend on the vulnerable Network library
Publicly accessible services consuming the affected versions

Discovery Timeline

2026-06-05 - CVE-2026-45290 published to NVD
2026-06-05 - Last updated in NVD database

Technical Details for CVE-2026-45290

Vulnerability Analysis

The vulnerability resides in how the Cloudburst Network library processes incoming network traffic on its Netty-based pipeline. An attacker who can reach the listening service over the network can submit crafted input that causes the Netty event loop thread to stall. Because Netty multiplexes many connections onto a small pool of event loop threads, stalling a single loop blocks processing for every connection assigned to it. This results in a denial of service condition impacting availability while leaving confidentiality and integrity untouched.

The issue maps to CWE-770: Allocation of Resources Without Limits or Throttling. The library accepts work onto the event loop without enforcing bounds that would prevent a single client from monopolizing the thread.

Root Cause

The root cause is the absence of proper throttling or resource limits on operations dispatched to the Netty event loop. Event loop threads must remain non-blocking to service all assigned channels. When the library performs unbounded work or accepts attacker-controlled input that triggers a blocking code path, the loop ceases to make progress and all dependent I/O stalls.

Attack Vector

Exploitation requires only network access to a publicly exposed service that embeds the vulnerable library. No authentication and no user interaction are required. An attacker sends crafted packets to the listening endpoint to trigger the stall condition on the event loop thread, after which legitimate clients can no longer be serviced.

No public proof-of-concept code has been released. Technical details are available in the GitHub Security Advisory GHSA-7x5h-rg5x-9gf3.

Detection Methods for CVE-2026-45290

Indicators of Compromise

Unresponsive Cloudburst-based services where the process remains running but stops accepting or processing connections
Netty event loop threads stuck in a non-progressing state visible in JVM thread dumps
Sudden drop in throughput on services using the Cloudburst Network library without a corresponding CPU spike

Detection Strategies

Inventory all applications and dependencies to identify use of the Cloudburst Network library and verify the loaded version against 1.0.0.CR3-20260417.085727-30
Capture periodic JVM thread dumps and alert when Netty EventLoop threads remain on the same stack frame across consecutive samples
Monitor application-level health checks and TCP-level liveness probes to detect listeners that stop responding while the process is alive

Monitoring Recommendations

Track connection acceptance rate, request latency, and event loop task queue depth as leading indicators of a stall
Log and rate-limit anomalous packet patterns at upstream proxies or firewalls fronting Cloudburst-based services
Correlate network traffic spikes from single sources with degradation in service responsiveness to identify exploitation attempts

How to Mitigate CVE-2026-45290

Immediate Actions Required

Upgrade the Cloudburst Network library to version 1.0.0.CR3-20260417.085727-30 or later in all dependent projects
Rebuild and redeploy any service that statically bundles the affected library version
Restrict network exposure of affected services to trusted sources until the upgrade is complete

Patch Information

The maintainers fixed the issue in Cloudburst Network version 1.0.0.CR3-20260417.085727-30. All consumers of the library must upgrade to at least this version. Refer to the GitHub Security Advisory GHSA-7x5h-rg5x-9gf3 for release details.

Workarounds

No workarounds exist beyond updating the library, according to the upstream advisory
Apply upstream rate limiting and connection throttling at network appliances to reduce attacker reach until patching is complete
Limit public exposure of services using the vulnerable library by placing them behind authenticated proxies or allowlists

bash

# Example Maven dependency update to the fixed version
# In pom.xml, set the Cloudburst Network dependency to the patched release:
#
# <dependency>
#   <groupId>org.cloudburstmc.netty</groupId>
#   <artifactId>network</artifactId>
#   <version>1.0.0.CR3-20260417.085727-30</version>
# </dependency>

mvn -U dependency:resolve
mvn clean package