EUVD-2026-82869
GHSA-fcr3-v77c-x7hx
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Unauthenticated single-packet remote trigger over the network (AV:N/AC:L/PR:N/UI:N) causing memory/CPU exhaustion with availability-only impact (A:H), no C/I effect.
Primary rating from Vendor (redhat).
CVSS VectorVendor: redhat
Lifecycle Timeline
5DescriptionCVE.org
Summary
Netty's fix for CVE-2026-44248 is incomplete. The decoder checks if the MQTT packet's Remaining Length exceeds maxBytesInMessage, but fails to validate the Properties Length against the Remaining Length. An attacker can bypass the size limit by sending a small Remaining Length but an enormous Properties Length. This forces Netty to buffer and parse millions of properties, allowing an unauthenticated remote attacker to trigger excessive memory and CPU consumption, leading to OutOfMemoryError.
Details
In io.netty.handler.codec.mqtt.MqttDecoder, the decodeProperties() helper method reads totalPropertiesLength and attempts to parse that many bytes. If the buffer lacks the full length, a Signal is thrown. The catch block inside decode() only enforces maxBytesInMessage against bytesRemainingBeforeVariableHeader (the packet's Remaining Length).
By sending a CONNECT packet with a small Remaining Length but a huge Properties Length, the size check passes. ReplayingDecoder then buffers data from the network until the huge Properties Length is reached, parsing millions of UserProperty objects and exhausting CPU and memory.
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Articles & Coverage 1
AnalysisAI
Denial of service in Netty's MQTT decoder lets unauthenticated remote attackers exhaust server memory and CPU by sending a crafted CONNECT packet whose Properties Length is enormous while its Remaining Length stays small, bypassing the maxBytesInMessage guard that was added to fix CVE-2026-44248. The issue affects any Netty pipeline that runs io.netty.handler.codec.mqtt.MqttDecoder and exposes an MQTT listener; downstream Red Hat products such as AMQ Broker 7, Fuse 7, JBoss EAP 7, Red Hat Single Sign-On 7, and Red Hat Build of Apache Camel for Spring Boot 4 are listed as affected. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the target application to run a Netty pipeline that includes io.netty.handler.codec.mqtt.MqttDecoder and to expose an MQTT listener reachable by the attacker - i.e., an MQTT broker/gateway endpoint accepting CONNECT packets. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine but bounded priority. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | No vendor-released patch identified at time of analysis. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory every MQTT listener across the affected Red Hat products (AMQ Broker 7, Fuse 7, JBoss EAP 7, Red Hat Single Sign-On 7, and Red Hat Build of Apache Camel for Spring Boot 4), determine which of those endpoints are reachable from untrusted or broad network ranges, and close or firewall any listener that does not have a documented business requirement to be externally reachable; where an MQTT listener cannot be removed, place it behind a connection-limiting proxy or load balancer that caps concurrent connections and inbound packet size, and enable memory/CPU alerting on those hosts so resource exhaustion is detected within minutes rather than after an outage. …
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External POC / Exploit Code
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