CVE-2026-76816
Netty: MQTT Topic Name and Client ID Validation Bypass
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.
Attack profile
How easy it is to exploit
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
3.5
Netty: MQTT Topic Name and Client ID Validation Bypass
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.
- Record
CVE-2026-76816- CVSS 3.1
- 3.5 Low
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-20, CWE-626
- Updated
- 2026-11-02
EUVDEUVD-2026-65093
3.5
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.
- Record
EUVD-2026-65093- CVSS 3.1
- 3.5 Low
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
NVD
3.5
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.
- Record
CVE-2026-76816- CVSS 3.1
- 3.5 Low
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-20, CWE-626
- Updated
- 2026-11-02
OSV
3.5
Netty: MQTT Topic Name and Client ID Validation Bypass
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.
- Record
CVE-2026-76816- CVSS 3.1
- 3.5 Low
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-20, CWE-626
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-76816
3.5
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.
- Record
DEBIAN-CVE-2026-76816- CVSS 3.1
- 3.5 Low
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-76816
3.5
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.
- Record
UBUNTU-CVE-2026-76816- CVSS 3.1
- 3.5 Low
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
OSVopenSUSE-SU-2026:11882-1 No score
netty-4.1.138-1.1 on GA media
These are all security issues fixed in the netty-4.1.138-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:11882-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:4391-1 No score
Security update for netty, netty-tcnative
This update for netty, netty-tcnative fixes the following issues:
- CVE-2026-59902: Netty: Memory Exhaustion in SctpMessageCompletionHandler (bsc#1275501).
- CVE-2026-59903: Netty Vulnerable to Cache Poisoning and Information Disclosure via CORS Vary Header Overwrite (bsc#1275500).
- CVE-2026-62243: TLS hostname verification bypass in Netty OpenSSL client path (bsc#1276455).
- CVE-2026-62380: null byte and CRLF injection in Socks4ClientEncoder and Socks5ClientEncoder (bsc#1276456).
- CVE-2026-75595: fragmented TLS
ClientHellocauses fallback to defaultSslContextand allows for SNI routing and mTLS requirement bypass (bsc#1276420). - CVE-2026-75596: fragmented
ClientHellorecords can trigger quadratic pre-handshake reassembly in default SNI parsing (bsc#1276421). - CVE-2026-76816: missing input validation in
MqttEncoderallows for null-byte injection, topic hijacking, and ACL bypassing (bsc#1277243). - CVE-2026-89044: HTTP request smuggling in Netty via improper validation of final Transfer-Encoding coding (bsc#1280048).
- CVE-2026-93488: Denial of Service via unbounded concurrent SPDY streams (bsc#1282084).
- CVE-2026-93491: Denial of Service via unbounded HttpServerCodec HTTP/1.1 pipeline queue (bsc#1282085).
- CVE-2026-93492: HTTP/2 HpackEncoder DoS with large table size (bsc#1282132).
- CVE-2026-93493: missing
nextUpdatefield in OCSP responses leads to silent validation bypass (bsc#1281431). - CVE-2026-93494: ByteBuf Leak in StompSubframeDecoder When a Frame Body Is Never Terminated (bsc#1282506).
- CVE-2026-93558: Unbounded Per-Connection Queue Growth in WebSocketServerExtensionHandler Leads to Denial of Service (bsc#1282140).
- CVE-2026-93560: STOMP codec content-length long-to-int truncation causes infinite decode loop DoS (bsc#1282141).
- CVE-2026-93562: Incomplete validation of malformed Transfer-Encoding allows HTTP request smuggling (bsc#1282362).
- CVE-2026-93563: unbounded multi-line response accumulation in
SmtpResponseDecoderleads to memory exhaustion and a DoS (bsc#1281432). - CVE-2026-93564: HAProxy PROXY-v2 nested-TLV grandchild ByteBuf reference-count leak (bsc#1282363).
- CVE-2026-93565: RtspDecoder Method-Token Smuggling via Trailing Control Byte (bsc#1282364).
- CVE-2026-93566: HTTP Request Smuggling due to control characters in the chunk-size line (bsc#1282366).
- CVE-2026-93567: HTTP/1 authority-form CONNECT is translated to malformed HTTP/2 CONNECT with Host-controlled :authority (bsc#1282367).
- CVE-2026-93568: HTTP/2 and HTTP/3 Extended CONNECT requests are downgraded as regular CONNECT requests (bsc#1282370).
- CVE-2026-93569: HTTP/1 absolute-form Host mismatch is translated to HTTP/2 :authority, overriding the request-target authority (bsc#1282372).
- CVE-2026-93572: multiplication of patched preallocation limits in
RedisArrayAggregatornested RESP headers can lead to denial of service (bsc#1281433). - CVE-2026-93573: Incomplete validation of malformed Transfer-Encoding allows HTTP request smuggling (bsc#1282373).
- CVE-2026-93574: HTTP request smuggling via post-digit whitespace in chunk-size parsing (bsc#1282374).
- CVE-2026-93575: missing validations in the
MqttDecodercan lead to excessive resource consumption and a DoS (bsc#1281434). - CVE-2026-93576: netty-codec-smtp -- SMTP command-name field is not CRLF-validated (bsc#1282507).
- CVE-2026-93578: missing Extended Key Usage (EKU) check in OCSP client allows certificate revocation bypass (bsc#1281435).
- CVE-2026-93579: HTTP/2 header field values are not validated by default (bsc#1282378).
Changes for netty:
- Upgrade to upstream version 4.1.138
Changes for netty-tcnative:
- Upgrade to version 2.0.84 Final
- Record
SUSE-SU-2026:4391-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
nettyDebian:12 |
All versions, plus listed versions 1:4.1.48-101:4.1.48-111:4.1.48-121:4.1.48-131:4.1.48-14 Show 7 moreShow less1:4.1.48-151:4.1.48-161:4.1.48-71:4.1.48-7+deb12u11:4.1.48-7+deb12u21:4.1.48-81:4.1.48-9 |
None known |
nettyDebian:13 |
All versions, plus listed versions 1:4.1.48-101:4.1.48-10+deb13u11:4.1.48-111:4.1.48-121:4.1.48-131:4.1.48-141:4.1.48-151:4.1.48-16 |
None known |
nettyDebian:14 |
All versions, plus listed versions 1:4.1.48-101:4.1.48-111:4.1.48-121:4.1.48-131:4.1.48-141:4.1.48-151:4.1.48-16 |
None known |
netty-tcnativeSUSE:Linux Enterprise Module for Development Tools 15 SP7 |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
nettySUSE:Linux Enterprise Module for Package Hub 15 SP7 |
before 4.1.138-150200.4.56.1 | 4.1.138-150200.4.56.1 |
netty-tcnativeSUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
netty-tcnativeSUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
netty-tcnativeSUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
netty-tcnativeSUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
netty-tcnativeSUSE:Linux Enterprise Server 15 SP4-LTSS |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
Show 14 moreShow less
| Package | Affected | Fixed |
|---|---|---|
netty-tcnativeSUSE:Linux Enterprise Server 15 SP5-LTSS |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
netty-tcnativeSUSE:Linux Enterprise Server 15 SP6-LTSS |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
netty-tcnativeSUSE:Linux Enterprise Server for SAP Applications 15 SP4 |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
netty-tcnativeSUSE:Linux Enterprise Server for SAP Applications 15 SP5 |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
netty-tcnativeSUSE:Linux Enterprise Server for SAP Applications 15 SP6 |
before 2.0.84-150200.3.51.1 | 2.0.84-150200.3.51.1 |
nettyUbuntu:Pro:14.04:LTS |
All versions, plus listed versions 1:3.2.6.Final-21:3.2.6.Final-2+deb8u2build0.14.04.1~esm11:3.2.6.Final-2+deb8u2ubuntu0.1~esm1 |
None known |
nettyUbuntu:Pro:16.04:LTS |
All versions, plus listed versions 1:3.2.6.Final-21:4.0.32-11:4.0.33-11:4.0.34-11:4.0.34-1ubuntu0.1~esm1 Show 4 moreShow less1:4.0.34-1ubuntu0.1~esm21:4.0.34-1ubuntu0.1~esm31:4.0.34-1ubuntu0.1~esm41:4.0.34-1ubuntu0.1~esm5 |
None known |
nettyUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 1:4.1.7-41:4.1.7-4ubuntu0.1~esm11:4.1.7-4ubuntu0.11:4.1.7-4ubuntu0.1+esm11:4.1.7-4ubuntu0.1+esm2 Show 5 moreShow less1:4.1.7-4ubuntu0.1+esm31:4.1.7-4ubuntu0.1+esm41:4.1.7-4ubuntu0.1+esm51:4.1.7-4ubuntu0.1+esm61:4.1.7-4ubuntu0.1+esm7 |
None known |
nettyUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 1:4.1.33-11:4.1.33-21:4.1.33-31:4.1.45-11:4.1.45-1ubuntu0.1~esm1 Show 5 moreShow less1:4.1.45-1ubuntu0.1~esm21:4.1.45-1ubuntu0.1~esm31:4.1.45-1ubuntu0.1~esm41:4.1.45-1ubuntu0.1~esm61:4.1.45-1ubuntu0.1~esm7 |
None known |
nettyUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 1:4.1.48-41:4.1.48-4+deb11u1build0.22.04.11:4.1.48-4+deb11u2build0.22.04.11:4.1.48-4+deb11u2ubuntu0.1~esm11:4.1.48-4+deb11u2ubuntu0.1~esm2 Show 5 moreShow less1:4.1.48-4+deb11u2ubuntu0.11:4.1.48-4+deb11u2ubuntu0.1+esm11:4.1.48-4+deb11u2ubuntu0.1+esm31:4.1.48-4+deb11u2ubuntu0.21:4.1.48-4+deb11u2ubuntu0.2+esm1 |
None known |
nettyUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 1:4.1.48-71:4.1.48-81:4.1.48-91:4.1.48-9ubuntu0.1~esm11:4.1.48-9ubuntu0.1~esm2 Show 6 moreShow less1:4.1.48-9ubuntu0.11:4.1.48-9ubuntu0.1+esm11:4.1.48-9ubuntu0.1+esm31:4.1.48-9ubuntu0.21:4.1.48-9ubuntu0.2+esm11:4.1.48-9ubuntu0.2+esm2 |
None known |
nettyUbuntu:26.10 |
All versions, plus listed versions 1:4.1.48-161:4.1.48-16ubuntu1 |
None known |
nettyUbuntu:Pro:26.04:LTS |
All versions, plus listed versions 1:4.1.48-101:4.1.48-111:4.1.48-121:4.1.48-131:4.1.48-141:4.1.48-161:4.1.48-16ubuntu0.1~esm2 |
None known |
nettyopenSUSE:Tumbleweed |
before 4.1.138-1.1 | 4.1.138-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-76816 is a low vulnerability (CVSS 3.5) in Netty, published August 24, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.17%, the 6th percentile. Fixed in netty-tcnative 2.0.84-150200.3.51.1.
References
github.com/netty/netty/security/advisories/GHSA-43fm-7cxg-hf3j
github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7
github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961
github.com/CVEProject/cvelistV5/tree/main/cves/2026/76xxx/CVE-2026-76816.json
nvd.nist.gov/vuln/detail/CVE-2026-76816
security-tracker.debian.org/tracker/CVE-2026-76816
Show 63 moreShow less
suse.com/support/update/announcement/2026/suse-su-20264391-1
bugzilla.suse.com/1275500
bugzilla.suse.com/1275501
bugzilla.suse.com/1276420
bugzilla.suse.com/1276421
bugzilla.suse.com/1276455
bugzilla.suse.com/1276456
bugzilla.suse.com/1277243
bugzilla.suse.com/1280048
bugzilla.suse.com/1281431
bugzilla.suse.com/1281432
bugzilla.suse.com/1281433
bugzilla.suse.com/1281434
bugzilla.suse.com/1281435
bugzilla.suse.com/1282084
bugzilla.suse.com/1282085
bugzilla.suse.com/1282132
bugzilla.suse.com/1282140
bugzilla.suse.com/1282141
bugzilla.suse.com/1282362
bugzilla.suse.com/1282363
bugzilla.suse.com/1282364
bugzilla.suse.com/1282366
bugzilla.suse.com/1282367
bugzilla.suse.com/1282370
bugzilla.suse.com/1282372
bugzilla.suse.com/1282373
bugzilla.suse.com/1282374
bugzilla.suse.com/1282378
bugzilla.suse.com/1282506
bugzilla.suse.com/1282507
suse.com/security/cve/CVE-2026-59902
suse.com/security/cve/CVE-2026-59903
suse.com/security/cve/CVE-2026-62243
suse.com/security/cve/CVE-2026-62380
suse.com/security/cve/CVE-2026-75595
suse.com/security/cve/CVE-2026-75596
suse.com/security/cve/CVE-2026-76816
suse.com/security/cve/CVE-2026-89044
suse.com/security/cve/CVE-2026-93488
suse.com/security/cve/CVE-2026-93491
suse.com/security/cve/CVE-2026-93492
suse.com/security/cve/CVE-2026-93493
suse.com/security/cve/CVE-2026-93494
suse.com/security/cve/CVE-2026-93558
suse.com/security/cve/CVE-2026-93560
suse.com/security/cve/CVE-2026-93562
suse.com/security/cve/CVE-2026-93563
suse.com/security/cve/CVE-2026-93564
suse.com/security/cve/CVE-2026-93565
suse.com/security/cve/CVE-2026-93566
suse.com/security/cve/CVE-2026-93567
suse.com/security/cve/CVE-2026-93568
suse.com/security/cve/CVE-2026-93569
suse.com/security/cve/CVE-2026-93572
suse.com/security/cve/CVE-2026-93573
suse.com/security/cve/CVE-2026-93574
suse.com/security/cve/CVE-2026-93575
suse.com/security/cve/CVE-2026-93576
suse.com/security/cve/CVE-2026-93578
suse.com/security/cve/CVE-2026-93579
ubuntu.com/security/CVE-2026-76816
cve.org/CVERecord?id=CVE-2026-76816