HTTP response splitting in Netty - CVE-2026-42578
Published: May 5, 2026
Vulnerability identifier: #VU130212
CSH Severity: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-42578
CWE-ID: CWE-113
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Netty
Netty
Software vendor:
Netty project
Netty project
Description
The vulnerability allows a remote attacker to inject arbitrary HTTP headers into CONNECT proxy requests.
The vulnerability exists due to improper neutralization of CRLF sequences in HTTP headers in io.netty.handler.proxy.HttpProxyHandler newInitialMessage() when handling user-influenced outbound headers. A remote attacker can supply crafted header values containing CRLF sequences to inject arbitrary HTTP headers into CONNECT proxy requests.
Exploitation requires an application to use HttpProxyHandler with user-influenced outboundHeaders without performing its own CRLF sanitization.
Remediation
Install security update from vendor's website.