CVE-2026-76816
Netty: MQTT Topic Name and Client ID Validation Bypass
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
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.
Timeline
ID reserved
By GitHub_M
- 5 days later
· 5 days later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Low3.5 | CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N |
| NVDNVD · Deferred | 3.1 | Low3.5 | CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.17% · top 93% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 3.5.
Weakness
Affected products
References (3)
- https://github.com/netty/netty/security/advisories/GHSA-43fm-7cxg-hf3j (opens in a new tab)x_refsource_CONFIRM
- https://github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7 (opens in a new tab)x_refsource_MISC
- https://github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-76816)Record last updated .