CVE-2026-42578

High

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Netty's HttpProxyHandler constructs HTTP CONNECT requests with header validation explicitly disabled. The newInitialMessage() method creates headers using DefaultHttpHeadersFactory.headersFactory().withValidation(false), then adds user-provided outboundHeaders without any CRLF validation. This allows an attacker who can influence the outbound headers to inject arbitrary HTTP headers into the CONNECT request sent to the proxy server. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

SeverityHigh

CVSS7.5

Exploit probability—

ProductNetty

PublishedMay 13, 2026

First seenMay 13, 2026

Weakness typeCWE-113CWE-113

How to fix

Update

netty netty4.1.133, 4.2.13 or later
io.netty:netty-handler-proxy4.1.133.Final, 4.2.13.Final or later

Vendor advisories

Affected products

Product	Affected versions	Fixed in
netty netty	v < 4.1.133, 4.2.0 ≤ v < 4.2.13	4.1.133, 4.2.13
io.netty:netty-handler-proxyMaven	v < 4.1.133.Final, 4.2.0.Alpha1 ≤ v < 4.2.13.Final	4.1.133.Final, 4.2.13.Final

Check your version

Choose the product and enter the version you run to see whether it falls in the affected range.

In the Intelligence 360 plan

Attack Surface Management

See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.