GHSA-jfg9-48mv-9qgx — netty-codec-mqtt
MEDIUMGHSA-jfg9-48mv-9qgx is a medium-severity (CVSS 5.3) Uncontrolled Resource Consumption vulnerability in io.netty:netty-codec-mqtt. A fix is available for io.netty:netty-codec-mqtt — see the affected versions and patch details below.
Netty MQTT: Resource exhaustion in MqttDecoder
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-jfg9-48mv-9qgx.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-jfg9-48mv-9qgx plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
io.netty:netty-codec-mqtt☕io.netty:netty-codec-mqttReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-mqtt | ≥ 4.2.0.Alpha1&&< 4.2.13.Final | 4.2.13.Finalio.netty:netty-codec-mqtt:4.2.13.Final |
| ☕Maven | io.netty:netty-codec-mqtt | all versions | 4.1.133.Finalio.netty:netty-codec-mqtt:4.1.133.Final |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-mqtt, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-codec-mqtt to 4.2.13.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jfg9-48mv-9qgx is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-jfg9-48mv-9qgx can be triaged on real exposure rather than presence alone.
Tailored to GHSA-jfg9-48mv-9qgx. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat AMQ Broker 7.13.6 | netty-codec-mqtt | RHSA-2026:66545 |
| Red Hat AMQ Broker 7.14.1 | netty-codec-mqtt | RHSA-2026:66488 |
| Red Hat build of Apache Camel 4.18.1.P1 for Spring Boot 3.5.16 | netty-codec-mqtt | RHSA-2026:37390 |
| Red Hat Data Grid 8.6.2 | netty-codec-mqtt | RHSA-2026:41951 |
Frequently Asked Questions
Is GHSA-jfg9-48mv-9qgx in your dependencies?
O3 Security finds GHSA-jfg9-48mv-9qgx across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.