Medium6.5Apache Software Foundation

Medium [CVE-2026-33523] HTTP response splitting vulnerability in multiple Apache HTTP Server modules with untrusted or compromised backend servers

This medium-severity Apache Software Foundation advisory covers CVE-2026-33523 affecting Apache HTTP Server.

CVE-2026-33523 Published May 4, 2026Updated by vendor Jun 17, 2026

CVE-2026-33523

Affected products & platforms

Apache Software FoundationHTTP Server

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Summary

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.

Affected versions

through 2.4.66

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Fixed versions

2.4.67

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Mitigation

Upgrade to a fixed release: 2.4.67. That is the remediation for this advisory.

The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Sources

Official and corroborating records used to build this advisory.

NVD discovery recordNVD
Independent discovery and scoring cross-reference. Vendor remediation guidance takes precedence. Discovered from the machine-readable feed https://services.nvd.nist.gov/rest/json/cves/2.0; this link opens the NVD record for CVE-2026-33523 instead of the raw feed document.
NIST National Vulnerability Database

Cross-references

Validate CVE metadata against the authoritative registries.

CVE-2026-33523NVD CVE.org MITRE

Official resources

Apache HTTP Server 2.4 vulnerabilities (official fixed-in table) (target: 2.4.67)
Official documentation
This advisory names 2.4.67 as the first fixed release — official upgrade documentation for Apache HTTP Server 2.4 vulnerabilities (official fixed-in table).
ASF Security — reporting & CVE process
Official documentation
The Apache Software Foundation's official security page: how ASF CVEs are published and where each project's advisories live.
Apache project downloads (fixed releases)
Official documentation
Official ASF download tree — fetch the fixed release named in this advisory from the project's directory.

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