CVE-2026-44248
This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.51%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public 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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.51% probability · 42th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-400, CWE-770
- Affected
- netty/netty
- Source
- security-advisories@github.com
References
- https://github.com/netty/netty/security/advisories/GHSA-jfg9-48mv-9qgxVendor Advisory
- https://access.redhat.com/errata/RHSA-2026:37390
- https://access.redhat.com/errata/RHSA-2026:41951
- https://access.redhat.com/errata/RHSA-2026:66488
- https://access.redhat.com/errata/RHSA-2026:66545
- https://access.redhat.com/security/cve/CVE-2026-44248
- https://bugzilla.redhat.com/show_bug.cgi?id=2477231
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44248.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.