CVE-2026-33523 Apache HTTP Server: multiple modules: HTTP response splitting forwarding malicious status line

What is CVE-2026-33523?

CVE-2026-33523 is a medium-severity vulnerability in Apache Http Server, published on 4 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

HTTP response splitting vulnerability in multiple Apache HTTP Server modules with untrusted or compromised backend servers.

This issue affects Apache HTTP Server: from through 2.4.66.

Users are recommended to upgrade to version 2.4.67, which fixes the issue.

Weakness: CWE-443

Which versions are affected by CVE-2026-33523?

1 open source package ship an affected version, including apache. It affects 1 product.

Products include Apache Http Server.

How do I fix CVE-2026-33523?

Upgrade apache to 2.4.67 or later.

Is CVE-2026-33523 being exploited?

There is no known exploitation of CVE-2026-33523 in the wild and no public exploit code.

Other vulnerabilities in Apache Http Server

• CVE-2021-42013 Apache HTTP Server Path Traversal Exploited Critical 9.8
• CVE-2024-38475 Apache HTTP Server Improper Escaping of Output Exploited Critical 9.1
• CVE-2021-40438 Apache HTTP Server-Side Request Forgery (SSRF) Exploited Critical 9.0
• CVE-2019-0211 Apache HTTP Server Privilege Escalation Exploited High 7.8
• CVE-2021-41773 Apache HTTP Server Path Traversal Exploited High 7.5

All Apache Http Server vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2026-33523, AZL-86022, BELL-CVE-2026-33523, BIT-apache-2026-33523, DEBIAN-CVE-2026-33523, GHSA-fc75-39v4-qm5p and 2 more.