Request splitting via HTTP/2 method injection and mod_proxy

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

No source has published a CVSS score for this record yet.

• CISA KEV Not listed.
• EPSS 0.46, the 98th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 16 Aug 2021. New records show when each source confirmed them.

Sources

• CVE List: CVE-2021-33193
• NVD: CVE-2021-33193

References from the CNA

• portswigger.net/research/http2
• github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch
• lists.apache.org/thread.html/re4162adc051c1a0a79e7a24093f3776373e8733abaff57253fef341d%40%3Ccvs.httpd.apache.org%3E mailing-list
• lists.apache.org/thread.html/ree7519d71415ecdd170ff1889cab552d71758d2ba2904a17ded21a70%40%3Ccvs.httpd.apache.org%3E mailing-list
• lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DSM6UWQICBJ2TU727RENU3HBKEAFLT6T/ vendor-advisory
• lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EUVJVRJRBW5QVX4OY3NOHZDQ3B3YOTSG/ vendor-advisory
• tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ vendor-advisory
• www.oracle.com/security-alerts/cpujan2022.html
• security.netapp.com/advisory/ntap-20210917-0004/
• www.tenable.com/security/tns-2021-17
• www.oracle.com/security-alerts/cpuapr2022.html
• security.gentoo.org/glsa/202208-20 vendor-advisory
• lists.debian.org/debian-lts-announce/2023/03/msg00002.html mailing-list

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.