Vulnerability · CVE-2026-33523
HTTP response splitting vulnerability in multiple Apache HTTP Server modules with untrusted or compromised backend servers.
Published May 4, 2026 · catalog updated Jun 17, 2026 · http server
Check if you run it
No confirmed exploitation is on record for CVE-2026-33523. EPSS is 0.44%. Act only if a listed version of http server is installed.
Gaps on this record
- No version range is stored. A customer cannot check an installed version against this record.
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- Medium6.5
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.44%
- Remediation
- Advisory link
- Affected products
- cpe apache/http server
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.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- cpe apache/http serverversion unspecified
How to fix CVE-2026-33523
Recommended remediation
A patch or advisory reference is linked. Open the original publisher for availability by product version.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-33523. EPSS is 0.44%. Act only if a listed version of http server is installed.
Which versions are affected?
Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-443. EPSS 0.44%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
May 4, 2026 · NIST NVD
Detected
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.
Jun 17, 2026 · NIST NVD
Updated
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.
Sources
- CVE.orgVulnerability recordCVE-2026-33523
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-33523
30-day exploitation probability 0.4%
first.org - NIST NVDVulnerability recordCVE-2026-33523
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.
nvd.nist.gov
References
Freshness
Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.