CVE-2021-33193

Updated: 2025-08-20 03:13:08.986634

Description:

A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.


Links NIST CIRCL RHEL Ubuntu

Severity

Severity Score
CVSS Version 2.x MEDIUM 5.0
CVSS Version 3.x HIGH 7.5

Status

OS name Project name Version Score Severity Status Errata Last updated

Statement

CentOS 6 ELS httpd 2.2.15 7.5 HIGH Not Vulnerable 2025-09-17 03:54:50 We’ve reasoned that this vulnerability is hard to use to cause significant impact on target system...
CentOS 8.4 ELS httpd 2.4.37 7.5 HIGH Released CLSA-2022:1654106434 2022-06-01 14:37:18 We’ve reasoned that this vulnerability is hard to use to cause significant impact on target system...
CentOS 8.5 ELS httpd 2.4.37 7.5 HIGH Released CLSA-2022:1654106630 2022-06-01 14:37:00 We’ve reasoned that this vulnerability is hard to use to cause significant impact on target system...
CloudLinux 6 ELS httpd 2.2.15 7.5 HIGH Ignored 2025-09-19 21:21:01 We’ve reasoned that this vulnerability is hard to use to cause significant impact on target system...
Oracle Linux 6 ELS httpd 2.2.15 7.5 HIGH Not Vulnerable 2025-09-17 03:54:48 We’ve reasoned that this vulnerability is hard to use to cause significant impact on target system...
Ubuntu 16.04 ELS apache2 2.4.18 7.5 HIGH Not Vulnerable 2025-10-24 09:05:46 We’ve reasoned that this vulnerability is hard to use to cause significant impact on target system...
Ubuntu 18.04 ELS apache2 2.4.29 7.5 HIGH Already Fixed 2025-10-22 22:04:01 We’ve reasoned that this vulnerability is hard to use to cause significant impact on target system...