This Red Hat security advisory addresses multiple high-severity vulnerabilities (CVSS scores 7.3-7.5) in the `mod_http2` module for Apache HTTP Server, including HTTP/2 denial-of-service via memory exhaustion or compression bombs, a use-after-free flaw allowing arbitrary code execution, and an out-of-bounds read. Affected Apache httpd versions are 2.4.17 through 2.4.63 for CVE-2025-53020 and 2.4.55 through 2.4.67 for CVE-2026-48913 and CVE-2026-49975. The fixed versions are Apache httpd 2.4.64 for CVE-2025-53020 and 2.4.68 for the other listed CVEs.
Red Hat Product Errata RHSA-2026:50538 - Security Advisory Issued: 2026-08-05 Updated: 2026-08-05 RHSA-2026:50538 - Security Advisory Overview Updated Packages Synopsis Important: mod_http2 security update Type/Severity Security Advisory: Important Red Hat Lightspeed patch analysis Identify and remediate systems affected by this advisory. View affected systems Topic An update for mod_http2 is now available for Red Hat Enterprise Linux 10.0 Extended Update Support. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section. Description The mod_h2 Apache httpd module implements the HTTP2 protocol (h2+h2c) on top of libnghttp2 for httpd 2.4 servers. Security Fix(es): mod_http2: Apache HTTP Server: HTTP/2 DoS by Memory Increase (CVE-2025-53020) httpd: httpd: HTTP/2 Remote Denial of Service via compression bomb and Slowloris-style attack (CVE-2026-49975) httpd: mod_http2: Apache HTTP Server mod_http2: Use After Free vulnerability allows arbitrary code execution or denial of service. (CVE-2026-48913) httpd: Apache HTTP Server: Out-of-bounds Read in mod_headers and mod_mime (CVE-2026-43951) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section. Solution For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 Affected Products Red Hat Enterprise Linux for x86_64 - Extended Update Support 10.0 x86_64 Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 10.0 s390x Red Hat Enterprise Linux for Power, little endian - Extended Update Support 10.0 ppc64le Red Hat Enterprise Linux for ARM 64 - Extended Update Support 10.0 aarch64 Red Hat Enterprise Linux for ARM 64 - 4 years of updates 10.0 aarch64 Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 10.0 s390x Red Hat Enterprise Linux for Power, little endian - 4 years of support 10.0 ppc64le Red Hat Enterprise Linux for x86_64 - 4 years of updates 10.0 x86_64 Fixes BZ - 2379343 - CVE-2025-53020 mod_http2: Apache HTTP Server: HTTP/2 DoS by Memory Increase BZ - 2485371 - CVE-2026-49975 httpd: httpd: HTTP/2 Remote Denial of Service via compression bomb and Slowloris-style attack BZ - 2486405 - CVE-2026-48913 httpd: mod_http2: Apache HTTP Server mod_http2: Use After Free vulnerability allows arbitrary code execution or denial of service. BZ - 2486415 - CVE-2026-43951 httpd: Apache HTTP Server: Out-of-bounds Read in mod_headers and mod_mime CVEs CVE-2025-53020 CVE-2026-43951 CVE-2026-48913 CVE-2026-49975 References https://access.redhat.com/security/updates/classification/#important The Red Hat security contact is secalert@redhat.com. More contact details at https://access.redhat.com/security/team/contact/.