CVE-2025-55163 in Netty
Summary
by MITRE • 08/13/2025
Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.124.Final and 4.2.4.Final, Netty is vulnerable to MadeYouReset DDoS. This is a logical vulnerability in the HTTP/2 protocol, that uses malformed HTTP/2 control frames in order to break the max concurrent streams limit - which results in resource exhaustion and distributed denial of service. This issue has been patched in versions 4.1.124.Final and 4.2.4.Final.
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Analysis
by VulDB Data Team • 01/21/2026
The vulnerability CVE-2025-55163 represents a critical logical flaw in the Netty networking framework that affects HTTP/2 protocol implementation. This vulnerability specifically targets the management of concurrent streams within HTTP/2 connections, creating a pathway for malicious actors to exploit the protocol's resource allocation mechanisms. The issue manifests as a MadeYouReset DDoS attack vector that leverages malformed HTTP/2 control frames to manipulate the maximum concurrent streams limit, ultimately leading to resource exhaustion and service disruption. The vulnerability exists in Netty versions prior to 4.1.124.Final and 4.2.4.Final, making these releases particularly susceptible to exploitation in production environments that rely on HTTP/2 communication protocols.
The technical implementation of this vulnerability exploits the HTTP/2 protocol's stream management logic by sending carefully crafted malformed control frames that manipulate the max concurrent streams parameter. This manipulation allows attackers to bypass normal connection limits and consume excessive resources, effectively creating a denial of service condition. The vulnerability operates at the protocol level rather than at the network layer, making it particularly insidious as it leverages legitimate protocol features to achieve malicious outcomes. The flaw demonstrates a weakness in how Netty handles stream limit enforcement during HTTP/2 connection establishment and maintenance, creating opportunities for attackers to exhaust available resources through controlled frame manipulation.
From an operational impact perspective, this vulnerability presents a significant threat to systems relying on Netty's HTTP/2 capabilities, particularly those handling high volumes of concurrent connections. The resource exhaustion resulting from this attack can lead to complete service unavailability, system instability, and potential cascading failures in distributed architectures. Organizations using Netty frameworks in web servers, application servers, or microservices environments face elevated risk, as the attack can be executed with relatively simple tools and requires minimal computational resources to generate substantial impact. The vulnerability's classification as a logical flaw means that traditional network-based DDoS mitigation strategies may prove ineffective, requiring protocol-level defensive measures.
The mitigation strategy for CVE-2025-55163 centers on upgrading to the patched versions 4.1.124.Final and 4.2.4.Final of the Netty framework. Organizations should prioritize immediate deployment of these updates across all affected systems, particularly those handling HTTP/2 traffic. Additionally, implementing network-level controls such as rate limiting for HTTP/2 control frames and monitoring for unusual stream limit behaviors can provide additional defensive layers. The vulnerability aligns with ATT&CK technique T1498.001 for resource exhaustion attacks and CWE-400 for unchecked resource consumption, highlighting the need for proper input validation and resource management in protocol implementations. Security teams should also consider implementing connection tracking mechanisms to detect anomalous stream limit behaviors that may indicate exploitation attempts.