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CVE-2026-42581

Netty is an asynchronous, event-driven network application framework.

Impact

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.

Affected packages

EcosystemPackageAffectedFixed in
mavenio.netty:netty-codec-http>= 4.2.0.Alpha1, <= 4.2.12.Final4.2.13.Final

Affected products

VendorProductAffected versions
NettyNetty
before 4.1.133
from 4.2.0 before 4.2.13

Weakness classification

CWE-444

References