CVE-2026-89044

MEDIUM 6.5

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

CVSS Score

6.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-444
Vendor	netty
Product	netty
Published	Sep 10, 2026

Stay Ahead of the Next One

Get instant alerts for netty netty

Be the first to know when new medium vulnerabilities affecting netty netty are published — delivered to Slack, Telegram or Discord.

Get Free Alerts → Free · No credit card · 60 sec setup

CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Affected Versions

netty / netty

4.1.133.Final < 4.1.138.Final 4.2.13.Final < 4.2.18.Final

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/netty/netty/security/advisories/GHSA-hcvj-94mj-jp5c github.com: https://github.com/netty/netty/commit/ca87393b0e9e13c493d213a268e727a6d44e1585 github.com: https://github.com/netty/netty/commit/640d4d3324f7b811a4903d0730c8ccb35500500c github.com: https://github.com/netty/netty/blob/netty-4.1.137.Final/codec-http/src/main/java/io/netty/handler/codec/http/HttpObjectDecoder.java#L866 github.com: https://github.com/netty/netty/releases/tag/netty-4.1.138.Final github.com: https://github.com/netty/netty/releases/tag/netty-4.2.18.Final github.com: https://github.com/netty/netty vulncheck.com: 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-http-request-smuggling-via-transfer-encoding

Credits

Yu Bao, PayPal Cyber Security Team dreamlike-ocean Michael-JRead