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Medium severity5.3GHSA Advisory· Published May 13, 2026· Updated May 18, 2026

CVE-2026-44248

CVE-2026-44248

Description

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.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
io.netty:netty-codec-mqttMaven
>= 4.2.0.Alpha1, < 4.2.13.Final4.2.13.Final
io.netty:netty-codec-mqttMaven
< 4.1.133.Final4.1.133.Final

Affected products

56

Patches

Vulnerability mechanics

References

4

News mentions

0

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