Netty MQTT: Resource exhaustion in MqttDecoder

高 7.5CVE-2026-44248 · GHSA-jfg9-48mv-9qgx · 13/05/2026 公開 · 26/10/2026 更新

要点

CVE-2026-44248 は io.netty:netty-codec-mqtt, netty (netty) に影響する深刻度「高」 (CVSS 7.5) の脆弱性です。
今後30日間に悪用される確率（EPSS）：0.56%（全脆弱性の 46.8% より高い）。
対処：4.2.13.Final, 4.1.133.Final, 4.2.13, 4.1.133 以降に更新してください。

パッケージ	影響を受けるバージョン	修正済みバージョン
io.netty:netty-codec-mqtt Maven	`≥ 4.2.0.Alpha1, < 4.2.13.Final< 4.1.133.Final`	`4.2.13.Final4.1.133.Final`
netty netty	`≥ 4.2.0, < 4.2.13< 4.1.133`	`4.2.134.1.133`

概要

Impact

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.

Resources

ANT-2026-09608 https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901027

NVD の説明

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.