TI-2026-53663 Aliases CVE-2026-76816

Netty: MQTT Topic Name and Client ID Validation Bypass

LOW 16CWE-20Published 2026-08-24 · Updated 2026-08-25

Key facts

Attack vector: Adjacent network
Privileges required: Low
User interaction: None
Attack complexity: Low
Impact type: —
Confidentiality · integrity · availability: None · Low · None
Fix status: Partial Red Hat: 5 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00174 6th percentileScored 2026-11-07

Fix Partial netty (netty): 4.1.137.FinalRed Hat: 5 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
netty	netty	4.2.0.Final to before 4.1.137.Final; before 4.1.137.Final	4.1.137.Final	Patch available	CNA

netty Vendornetty Affected 4.2.0.Final to before 4.1.137.Final; before 4.1.137.Final Fixed in 4.1.137.Final Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:netty:netty::::::::	—	—	netty

cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:* Versions — — ·netty

Remediation

Fix · CNA netty (netty) Fixed in 4.1.137.Final

Vendor assessments

Red Hat

Red Hat rating: Low. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat AMQ Broker 7	Affected	No fix yet: Fix deferred
Red Hat Fuse 7	Affected	No fix planned: Out of support scope
Red Hat JBoss Enterprise Application Platform 7	Affected	No fix planned: Out of support scope
Red Hat Single Sign-On 7	Affected	No fix planned: Out of support scope
Red Hat build of Apache Camel for Spring Boot 4	Affected	No fix yet: Fix deferred

Timeline

2026-10-02 Threatist record created from CVE-2026-76816

References

Other 3

TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
TI-2026-30861 Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization CVSS 3.1CRITICAL 9.8
TI-2026-30864 Netty: HttpClientCodec response desynchronization CVSS 3.1CRITICAL 9.1
TI-2026-30859 Netty: DNS Codec Input Validation Bypass in Netty (Encoder + Decoder) CVSS 3.1CRITICAL 9.1
TI-2026-64821 Netty 4.2.11 through 4.2.17 QUIC Hostname Verification Bypass CVSS 4.0HIGH 8.7
TI-2026-64818 Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS CVSS 4.0HIGH 8.7

See all 114 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences