{"id":"UBUNTU-CVE-2021-33193","details":"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.","modified":"2026-04-22T14:47:01.604312Z","published":"2021-08-16T08:15:00Z","related":["USN-5090-1"],"upstream":["CVE-2021-33193"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-33193"},{"type":"REPORT","url":"https://portswigger.net/research/http2"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-5090-1"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-33193"}],"affected":[{"package":{"name":"apache2","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/apache2@2.4.29-1ubuntu4.17?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.29-1ubuntu4.17"}]}],"versions":["2.4.27-2ubuntu3","2.4.29-1ubuntu1","2.4.29-1ubuntu2","2.4.29-1ubuntu3","2.4.29-1ubuntu4","2.4.29-1ubuntu4.1","2.4.29-1ubuntu4.2","2.4.29-1ubuntu4.3","2.4.29-1ubuntu4.4","2.4.29-1ubuntu4.5","2.4.29-1ubuntu4.6","2.4.29-1ubuntu4.7","2.4.29-1ubuntu4.8","2.4.29-1ubuntu4.10","2.4.29-1ubuntu4.11","2.4.29-1ubuntu4.12","2.4.29-1ubuntu4.13","2.4.29-1ubuntu4.14","2.4.29-1ubuntu4.16"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"apache2","binary_version":"2.4.29-1ubuntu4.17"},{"binary_version":"2.4.29-1ubuntu4.17","binary_name":"apache2-bin"},{"binary_name":"apache2-data","binary_version":"2.4.29-1ubuntu4.17"},{"binary_name":"apache2-suexec-custom","binary_version":"2.4.29-1ubuntu4.17"},{"binary_name":"apache2-suexec-pristine","binary_version":"2.4.29-1ubuntu4.17"},{"binary_name":"apache2-utils","binary_version":"2.4.29-1ubuntu4.17"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33193.json"}},{"package":{"name":"apache2","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/apache2@2.4.41-4ubuntu3.5?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.41-4ubuntu3.5"}]}],"versions":["2.4.41-1ubuntu1","2.4.41-4ubuntu1","2.4.41-4ubuntu2","2.4.41-4ubuntu3","2.4.41-4ubuntu3.1","2.4.41-4ubuntu3.3","2.4.41-4ubuntu3.4"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"apache2","binary_version":"2.4.41-4ubuntu3.5"},{"binary_name":"apache2-bin","binary_version":"2.4.41-4ubuntu3.5"},{"binary_name":"apache2-data","binary_version":"2.4.41-4ubuntu3.5"},{"binary_name":"apache2-suexec-custom","binary_version":"2.4.41-4ubuntu3.5"},{"binary_name":"apache2-suexec-pristine","binary_version":"2.4.41-4ubuntu3.5"},{"binary_name":"apache2-utils","binary_version":"2.4.41-4ubuntu3.5"},{"binary_name":"libapache2-mod-md","binary_version":"2.4.41-4ubuntu3.5"},{"binary_name":"libapache2-mod-proxy-uwsgi","binary_version":"2.4.41-4ubuntu3.5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33193.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}