CVE-2026-89044
Medium
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.
SeverityMedium
CVSS6.5
Exploit probability—
ProductNetty
PublishedSep 10, 2026
First seenSep 10, 2026
Weakness typeCWE-444CWE-444
How to fix
Update
- netty netty4.1.138, 4.2.18 or later
Patches
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| netty netty | 4.1.133 ≤ v < 4.1.138, 4.2.13 ≤ v < 4.2.18 | 4.1.138, 4.2.18 |
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