In certain proxy configurations, a denial of service attack against Apache HTTP Server versions 2.4.26 through to 2.4.63 can be triggered by untrusted clients causing an assertion in mod_proxy_http2.
Configurations affected are a reverse proxy is configured for an HTTP/2 backend, with ProxyPreserveHost set to "on".
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alma_linux | — | Upgrade mod_mdUpgrade mod_sslUpgrade mod_sessionUpgrade httpd-develUpgrade httpdUpgrade httpd-manualUpgrade mod_proxy_htmlUpgrade mod_ldapUpgrade httpd-filesystemUpgrade httpd-toolsUpgrade mod_http2 | Sep 3, 2025 | Sep 2, 2025 |
| Alpine Linux | — | Upgrade apache2 | Aug 8, 2025 | Jul 10, 2025 |
| Amazon Linux Ami 2 | — | Upgrade httpd-manualUpgrade mod_ldapUpgrade httpd-debuginfoUpgrade httpd-filesystemUpgrade mod_sessionUpgrade mod_sslUpgrade mod_mdUpgrade httpd-develUpgrade httpdUpgrade mod_proxy_htmlUpgrade httpd-tools | May 20, 2026 | May 20, 2026 |
| Amazon_linux_2023 | — | Upgrade httpd-debugsourceUpgrade httpd-manualUpgrade httpd-tools-debuginfoUpgrade mod_luaUpgrade mod_lua-debuginfoUpgrade httpd-develUpgrade httpd-toolsUpgrade httpd-debuginfoUpgrade httpd-coreUpgrade httpdUpgrade mod_sessionUpgrade mod_sslUpgrade mod_ldap-debuginfoUpgrade mod_session-debuginfoUpgrade mod_proxy_html-debuginfoUpgrade mod_proxy_htmlUpgrade mod_ssl-debuginfoUpgrade httpd-filesystemUpgrade mod_ldapUpgrade httpd-core-debuginfo | Aug 5, 2025 | Jul 14, 2025 |
| Apache Httpd | — | Upgrade to the latest version of Apache HTTPD | Jul 18, 2025 | Jul 10, 2025 |
| Debian | — | Upgrade apache2 | Jul 14, 2025 | Jul 10, 2025 |
| Freebsd | — | Upgrade mod_http2Upgrade apache24 | Jul 13, 2025 | Jul 11, 2025 |
| Gentoo Linux | — | Upgrade www-servers/apache. | Aug 16, 2026 | Aug 13, 2026 |
| Huawei Euleros 2_0_sp10 | — | Upgrade mod_http2 | Nov 12, 2025 | Oct 23, 2025 |
| Huawei Euleros 2_0_sp11 | — | Upgrade mod_http2 | Dec 12, 2025 | Oct 23, 2025 |
| Huawei Euleros 2_0_sp12 | — | Upgrade mod_http2 | Nov 12, 2025 | Oct 23, 2025 |
| Huawei Euleros 2_0_sp13 | — | Upgrade httpd-toolsUpgrade httpd-filesystemUpgrade httpdUpgrade mod_ssl | Oct 24, 2025 | Oct 23, 2025 |
| Oracle_linux | — | Upgrade mod_sessionUpgrade mod_sslUpgrade httpd-manualUpgrade httpd-develUpgrade mod_proxy_htmlUpgrade httpdUpgrade mod_mdUpgrade mod_ldapUpgrade httpd-toolsUpgrade httpd-filesystemUpgrade mod_http2 | Aug 27, 2025 | Jul 14, 2025 |
| Redhat_linux | — | Upgrade mod_http2Upgrade httpd-filesystemUpgrade mod_session-debuginfoUpgrade mod_ldapUpgrade httpd-tools-debuginfoUpgrade mod_sessionUpgrade httpd-debugsourceUpgrade httpd-toolsUpgrade mod_proxy_html-debuginfoUpgrade mod_ldap-debuginfoUpgrade httpdUpgrade httpd-manualUpgrade httpd-develUpgrade mod_ssl-debuginfoUpgrade mod_sslUpgrade mod_http2-debugsourceUpgrade mod_mdUpgrade mod_proxy_htmlUpgrade mod_md-debuginfoUpgrade mod_md-debugsourceUpgrade mod_http2-debuginfoUpgrade httpd-debuginfo | Jul 15, 2025 | Jul 10, 2025 |
| Rocky_linux | — | Upgrade mod_http2Upgrade httpd-tools-debuginfoUpgrade httpd-toolsUpgrade mod_ssl-debuginfoUpgrade mod_md-debugsourceUpgrade mod_http2-debugsourceUpgrade mod_mdUpgrade mod_proxy_html-debuginfoUpgrade mod_proxy_htmlUpgrade mod_ldapUpgrade httpd-debuginfoUpgrade httpdUpgrade httpd-develUpgrade mod_session-debuginfoUpgrade mod_md-debuginfoUpgrade mod_ldap-debuginfoUpgrade mod_sslUpgrade httpd-debugsourceUpgrade mod_http2-debuginfoUpgrade mod_session | Feb 5, 2026 | Sep 8, 2025 |
| Suse | — | Upgrade apache2-develUpgrade apache2Upgrade apache2-tls13-preforkUpgrade apache2-manualUpgrade apache2-tls13-docUpgrade apache2-tls13-utilsUpgrade apache2-example-pagesUpgrade apache2-workerUpgrade apache2-tls13-develUpgrade apache2-eventUpgrade apache2-utilsUpgrade apache2-tls13Upgrade apache2-preforkUpgrade apache2-tls13-workerUpgrade apache2-docUpgrade apache2-tls13-example-pages | Dec 5, 2025 | Sep 2, 2025 |
| Ubuntu | — | Upgrade apache2 (Ubuntu Pro)Upgrade apache2 | Jul 17, 2025 | Jul 10, 2025 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Aug 11, 2025 | Jul 10, 2025 |
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