CVE-2021-33193
Request splitting via HTTP/2 method injection and mod_proxy
At a glance
- Severity
- Not available
- EPSS
- EPSS 46.18 % · percentile 99 (2026-10-27)
- State
- PUBLISHED
- Published
- Updated
- Assigner
- apache
- NVD status
- Analyzed
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.
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N | NVD · nvd@nist.gov (Primary) |
| CVSS 2.0 | MEDIUM 5.0 | AV:N/AC:L/Au:N/C:N/I:P/A:N | NVD · nvd@nist.gov (Primary) |
European references
- ENISA EUVD · EUVD-2021-19907
- GCVE · GCVE-0-2021-33193
CERT-FR advisories
- CERTFR-2024-AVI-0575 — Multiples vulnérabilités dans les produits Juniper Networks · cert.ssi.gouv.fr
- CERTFR-2021-AVI-931 — Multiples vulnérabilités dans les produits Cisco · cert.ssi.gouv.fr
- CERTFR-2021-AVI-875 — Multiples vulnérabilités dans les produits Check Point · cert.ssi.gouv.fr
- CERTFR-2021-AVI-800 — Multiples vulnérabilités dans Tenable.sc · cert.ssi.gouv.fr
- CERTFR-2021-AVI-713 — Multiples vulnérabilités dans Apache httpd · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*≥ 2.4.17 < 2.4.49cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*cpe:2.3:a:tenable:tenable.sc:*:*:*:*:*:*:*:*≤ 5.19.1cpe:2.3:a:oracle:secure_backup:*:*:*:*:*:*:*:*< 18.1.0.1.0cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*
Affected products
| Product | Versions |
|---|---|
| Apache Software Foundation · Apache HTTP Server | affected Apache HTTP Server 2.4 2.4.17 to 2.4.48 |
References
- https://portswigger.net/research/http2
- https://github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch
- https://lists.apache.org/thread.html/re4162adc051c1a0a79e7a24093f3776373e8733abaff57253fef341d%40%3Ccvs.httpd.apache.org%3E
- https://lists.apache.org/thread.html/ree7519d71415ecdd170ff1889cab552d71758d2ba2904a17ded21a70%40%3Ccvs.httpd.apache.org%3E
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DSM6UWQICBJ2TU727RENU3HBKEAFLT6T/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EUVJVRJRBW5QVX4OY3NOHZDQ3B3YOTSG/
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://security.netapp.com/advisory/ntap-20210917-0004/
- https://www.tenable.com/security/tns-2021-17
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://security.gentoo.org/glsa/202208-20
- https://lists.debian.org/debian-lts-announce/2023/03/msg00002.html
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |