Vulnerability · Published Sep 10, 2026 · Assigned by VulnCheck
CVE-2026-89044Netty 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final HTTP Request Smuggling via Transfer-Encoding
Medium 6.5
In plain English
A medium-severity security flaw in netty from netty. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities).
Official description
Netty versions 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final fail to properly validate the final transfer coding in the Transfer-Encoding header, allowing attackers to smuggle requests by using malformed encoding declarations. Attackers can split Transfer-Encoding headers across multiple lines or use values like 'chunked, xchunked' to bypass validation and decode messages as chunked when the final coding is not chunked, enabling request smuggling attacks.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | netty | no fix listed | DEBIAN-CVE-2026-89044 |
| Debian:13 | netty | no fix listed | DEBIAN-CVE-2026-89044 |
| Debian:14 | netty | no fix listed | DEBIAN-CVE-2026-89044 |
| Ubuntu:26.10 | netty | no fix listed | UBUNTU-CVE-2026-89044 |
Affected products (as reported)
Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
References
- GitHub Security Advisory (GHSA-hcvj-94mj-jp5c) vendor-advisory
- Fix commit on the 4.1 branch: match the final transfer-coding token exactly patch
- Fix commit on the 4.2 branch patch
- Suffix-based chunked-must-be-last check at netty-4.1.137.Final technical-description
- netty netty-4.1.138.Final Release Notes release-notes
- netty netty-4.2.18.Final Release Notes release-notes
- netty/netty product
- VulnCheck Advisory: Netty 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final HTTP Request Smuggling via Transfer-Encoding third-party-advisory