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Vulnerability record · CVE-2026-89044 · published 10 September 2026

CVE-2026-89044: Netty http request smuggling vulnerability

Netty · Netty

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.

6.9 CVSS 4.0 Medium EPSS 0.43% · top 65.5% CWE-444 · HTTP request smuggling
6.9CVSS 4.0 base score
0.43%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References, 1 tagged exploit
18 Sep 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/netty/netty Product
https://github.com/netty/netty/blob/netty-4.1.137.Final/codec-http/src/main/java/io/netty/handler/codec/http/HttpObjectD Product
https://github.com/netty/netty/commit/640d4d3324f7b811a4903d0730c8ccb35500500c Patch
https://github.com/netty/netty/commit/ca87393b0e9e13c493d213a268e727a6d44e1585 Patch
https://github.com/netty/netty/releases/tag/netty-4.1.138.Final Release Notes
https://github.com/netty/netty/releases/tag/netty-4.2.18.Final Release Notes
https://github.com/netty/netty/security/advisories/GHSA-hcvj-94mj-jp5c ExploitVendor Advisory
https://www.vulncheck.com/advisories/netty-4.1.133-final-through-4.1.137-final-and-4.2.13-final-through-4.2.17-final-htt PatchThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-89044), CISA KEV, FIRST EPSS (scores of 2026-09-30). This page is refreshed as NVD updates the record.