Vulnerability in Netty
CVE-2026-89044
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.
Vulnerability class: HTTP Request Smuggling
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
Affected products
Weakness classification (CWE)
References
- disclosure@vulncheck.com (vendor-advisory)
- disclosure@vulncheck.com (patch)
- disclosure@vulncheck.com (patch)
- disclosure@vulncheck.com (technical-description)
- disclosure@vulncheck.com (release-notes)
- disclosure@vulncheck.com (release-notes)
- disclosure@vulncheck.com (product)
- disclosure@vulncheck.com (third-party-advisory)
Frequently asked questions
- What is CVE-2026-89044?
- CVE-2026-89044 is a medium-severity vulnerability in Netty, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 6.5/10. Published 2026-09-10.
- How severe is CVE-2026-89044?
- Medium severity. CVSS v3 base score is 6.5 out of 10.