High severity7.5NVD Advisory· Published Aug 16, 2021· Updated Jun 17, 2026
CVE-2021-33193
CVE-2021-33193
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected products
342.4.17 - 2.4.48+ 1 more
- (no CPE)range: 2.4.17 - 2.4.48
- (no CPE)range: Apache HTTP Server 2.4 2.4.17 to 2.4.48
- osv-coords32 versionspkg:bitnami/apachepkg:rpm/almalinux/httpdpkg:rpm/almalinux/httpd-develpkg:rpm/almalinux/httpd-filesystempkg:rpm/almalinux/httpd-manualpkg:rpm/almalinux/httpd-toolspkg:rpm/almalinux/mod_http2pkg:rpm/almalinux/mod_ldappkg:rpm/almalinux/mod_mdpkg:rpm/almalinux/mod_proxy_htmlpkg:rpm/almalinux/mod_sessionpkg:rpm/almalinux/mod_sslpkg:rpm/opensuse/apache2&distro=openSUSE%20Leap%2015.2pkg:rpm/opensuse/apache2&distro=openSUSE%20Leap%2015.3pkg:rpm/suse/apache2&distro=SUSE%20Enterprise%20Storage%206pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP1-ESPOSpkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP1-LTSSpkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015-ESPOSpkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015-LTSSpkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Basesystem%2015%20SP2pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Basesystem%2015%20SP3pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Package%20Hub%2015%20SP3pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Server%20Applications%2015%20SP2pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Server%20Applications%2015%20SP3pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Server%2012%20SP5pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Server%2015%20SP1-BCLpkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Server%2015%20SP1-LTSSpkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Server%2015-LTSSpkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2012%20SP5pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2015pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2015%20SP1pkg:rpm/suse/apache2&distro=SUSE%20Linux%20Enterprise%20Software%20Development%20Kit%2012%20SP5
>= 2.4.17, < 2.4.49+ 31 more
- (no CPE)range: >= 2.4.17, < 2.4.49
- (no CPE)range: < 2.4.37-47.module_el8.6.0+2935+fb177b09.2
- (no CPE)range: < 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma
- (no CPE)range: < 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma
- (no CPE)range: < 2.4.37-47.module_el8.6.0+2935+fb177b09.2
- (no CPE)range: < 2.4.37-47.module_el8.6.0+2935+fb177b09.2
- (no CPE)range: < 1.15.7-5.module_el8.6.0+2872+fe0ff7aa
- (no CPE)range: < 2.4.37-47.module_el8.6.0+2935+fb177b09.2
- (no CPE)range: < 1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa
- (no CPE)range: < 1:2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma
- (no CPE)range: < 2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma
- (no CPE)range: < 1:2.4.37-47.module_el8.6.0+2872+fe0ff7aa.1.alma
- (no CPE)range: < 2.4.43-lp152.2.18.1
- (no CPE)range: < 2.4.43-3.25.1
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.43-3.25.1
- (no CPE)range: < 2.4.43-3.25.1
- (no CPE)range: < 2.4.43-3.25.1
- (no CPE)range: < 2.4.43-3.25.1
- (no CPE)range: < 2.4.43-3.25.1
- (no CPE)range: < 2.4.23-29.77.2
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.23-29.77.2
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.33-3.55.1
- (no CPE)range: < 2.4.23-29.77.2
Patches
Vulnerability mechanics
References
13- github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patchnvdPatch
- lists.apache.org/thread.html/re4162adc051c1a0a79e7a24093f3776373e8733abaff57253fef341d%40%3Ccvs.httpd.apache.org%3EnvdPatch
- lists.apache.org/thread.html/ree7519d71415ecdd170ff1889cab552d71758d2ba2904a17ded21a70%40%3Ccvs.httpd.apache.org%3EnvdPatch
- www.oracle.com/security-alerts/cpuapr2022.htmlnvdPatchThird Party Advisory
- www.oracle.com/security-alerts/cpujan2022.htmlnvdPatchThird Party Advisory
- portswigger.net/research/http2nvdExploitThird Party Advisory
- lists.debian.org/debian-lts-announce/2023/03/msg00002.htmlnvdMailing ListThird Party Advisory
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DSM6UWQICBJ2TU727RENU3HBKEAFLT6T/nvdThird Party Advisory
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EUVJVRJRBW5QVX4OY3NOHZDQ3B3YOTSG/nvdThird Party Advisory
- security.gentoo.org/glsa/202208-20nvdThird Party Advisory
- security.netapp.com/advisory/ntap-20210917-0004/nvdThird Party Advisory
- tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQnvdThird Party Advisory
- www.tenable.com/security/tns-2021-17nvdThird Party Advisory
News mentions
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