Netty: MQTT Topic Name and Client ID Validation Bypass

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-76816
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-24 20:17:19 UTC
Updated2026-08-24 20:17:19 UTC
DescriptionNetty is an asynchronous, event-driven network application framework. Prior to versions 4.1.137.Final and 4.2.17.Final, MqttEncoder does not validate client identifiers, will topics, usernames, and PUBLISH topic names before encoding, allowing prohibited null bytes in MQTT UTF-8 string fields and potentially causing routing, access-control, or identity mismatches in downstream brokers. The vulnerability is exploitable when an application uses Netty's MQTT encoder to construct messages from user-controlled input. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

Risk And Classification

Primary CVSS: v3.1 3.5 LOW from [email protected]

CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Problem Types: CWE-20 | CWE-626 | CWE-20 CWE-20: Improper Input Validation | CWE-626 CWE-626: Null Byte Interaction Error (Poison Null Byte)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary3.5LOWCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
3.1CNADECLARED3.5LOWCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Netty Netty affected >= 4.2.0.Final, < 4.1.137.Final Not specified
CNA Netty Netty affected < 4.1.137.Final Not specified

References

ReferenceSourceLinkTags
github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7 [email protected] github.com
github.com/netty/netty/security/advisories/GHSA-43fm-7cxg-hf3j [email protected] github.com
github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961 [email protected] github.com
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