CVE-2026-44248

Netty: Resource exhaustion in MqttDecoder

HIGH

7.5

CVSS Score

Published: May 13, 2026 at 06:23 PM UTC

Updated: October 26, 2026 at 05:10 PM UTC

4 products affected across 3 vendorsNettyNettyFuse

Using netty by netty?

Get instant alerts when new vulnerabilities affect netty - before attackers find them.

Real-time alertsTrack your software stackFree plan available

Start Free Sign In

Severity

HIGH7.5

Exploit prediction

EPSS 0.6%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Netty · Nettymaven

95%

v < 4.1.1334.2.0 ≤ v < 4.2.13

Affected range stops below 4.1.133, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.1.133.Final, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.13.Final, so it looks safe — our inference, not a vendor statement

Netty · Io Netty

90%

v < 4.1.133.Final4.2.0.Alpha1 ≤ v < 4.2.13.Final

Affected range stops below 4.1.133.Final, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.13.Final, so it looks safe — our inference, not a vendor statement

Fuse · Red Hatrpm

60%

Process Automation · Red Hatrpm

60%

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/netty/netty/security/advisories/GHSA-jfg9-48mv-9qgx