CVE-2026-42578
Published:May 13, 2026
Updated:May 18, 2026
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.
Affected Packages
https://github.com/netty/netty.git (GITHUB):
Affected version(s) >=netty-3.2.4.Final <netty-4.1.133.FinalFix Suggestion:
Update to version netty-4.1.133.Finalhttps://github.com/netty/netty.git (GITHUB):
Affected version(s) >=netty-4.2.0.Alpha1 <netty-4.2.13.FinalFix Suggestion:
Update to version netty-4.2.13.Finalio.netty:netty-handler-proxy (JAVA):
Affected version(s) >=4.1.0.Beta4 <4.1.133.FinalFix Suggestion:
Update to version 4.1.133.Finalio.netty:netty-handler-proxy (JAVA):
Affected version(s) >=4.2.0.Alpha1 <4.2.13.FinalFix Suggestion:
Update to version 4.2.13.FinalRelated Resources (4)
Do you need more information?
Contact UsCVSS v4
Base Score:
2.9
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
Exploit Maturity
POC
CVSS v3
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
EPSS
Base Score:
0.05