Netty <4.2.13.Final/4.1.133.Final MQTT 5 Properties Buffering Resource Exhaustion
CVE-2026-44248 Published on May 13, 2026
Netty: Resource exhaustion in MqttDecoder
Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, the MQTT 5 header Properties section is parsed and buffered before any message size limit is applied. Specifically, in MqttDecoder, the decodeVariableHeader() method is called before the bytesRemainingBeforeVariableHeader > maxBytesInMessage check. The decodeVariableHeader() can call other methods which will call decodeProperties(). Effectively, Netty does not apply any limits to the size of the properties being decoded. Additionally, because MqttDecoder extends ReplayingDecoder, Netty will repeatedly re-parse the enormous Properties sections and buffer the bytes in memory, until the entire thing parses to completion. This can cause high resource usage in both CPU and memory. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.
Vulnerability Analysis
CVE-2026-44248 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a small impact on availability.
Weakness Type
What is a Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-44248 has been classified to as a Resource Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-44248
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Affected Versions
netty:- Version >= 4.2.0.Alpha1, < 4.2.13.Final is affected.
- Version < 4.1.133.Final is affected.
- Version >= 4.2.0.Alpha1, < 4.2.13.Final is affected.
- Version < 4.1.133.Final is affected.