CVE-2026-42581

MEDIUM

Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization

Title source: cna
STIX 2.1

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving Content-Length intact in the forwarded HttpMessage. Any downstream proxy or handler that trusts Content-Length over Transfer-Encoding will disagree on message boundaries, enabling request smuggling. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

References (1)

Core 1
Core References

Scores

CVSS v3 5.8
EPSS 0.0040
EPSS Percentile 31.6%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable yes
Technical Impact partial

Details

CWE
CWE-444
Status published
Products (5)
io.netty/netty-codec-http 0 - 4.1.133.FinalMaven
io.netty/netty-codec-http 4.2.0.Alpha1 - 4.2.13.FinalMaven
netty/netty < 4.1.133
netty/netty < 4.1.133.Final
netty/netty >= 4.2.0.Alpha1, < 4.2.13.Final
Published May 13, 2026
Tracked Since May 14, 2026