23 Oct 2026 15:48:27 UTC
Netty: Resource exhaustion in MqttDecoder
cve-program · CVE-2026-44248 · Published
CVE-2026-44248
Netty: Resource exhaustion in MqttDecoder
CVSS 3.1 5.3 MEDIUMCheck source for fixed versionsKEV status unknown
cve-program · CVE-2026-44248
PublishedNetty 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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