CVE-2026-44248
Publication date 13 May 2026
Last updated 6 June 2026
Ubuntu priority
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| netty | 26.04 LTS resolute |
Vulnerable
|
| 25.10 questing |
Vulnerable
|
|
| 24.04 LTS noble |
Vulnerable
|
|
| 22.04 LTS jammy |
Vulnerable
|
|
| 20.04 LTS focal |
Vulnerable
|
|
| 18.04 LTS bionic |
Vulnerable
|
|
| 14.04 LTS trusty |
Vulnerable
|
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
5.3 · Medium
|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | None |
| Integrity impact | None |
| Availability impact | Low |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |