CVE-2026-76816
Netty: MQTT Topic Name and Client ID Validation Bypass
CVSS Score
3.5
EPSS Score
0.0%
EPSS Percentile
0th
Netty 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.
| CWE | CWE-20 CWE-626 |
| Vendor | netty |
| Product | netty |
| Published | Aug 24, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None
Affected Versions
netty / netty
>= 4.2.0.Final, < 4.1.137.Final < 4.1.137.Final