HTTP response splitting in Apache HTTP Server - CVE-2026-33523
Published: May 4, 2026
Vulnerability identifier: #VU129543
CSH Severity: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-33523
CWE-ID: CWE-113
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Apache HTTP Server
Apache HTTP Server
Software vendor:
Apache Foundation
Apache Foundation
Description
The vulnerability allows a remote attacker to manipulate HTTP responses.
The vulnerability exists due to improper neutralization of CRLF sequences in multiple Apache HTTP Server modules when forwarding a backend status line. A remote attacker can supply a malicious backend response to manipulate HTTP responses.
Exploitation requires an untrusted or compromised backend server.
Remediation
Install security update from vendor's website.