RHSA-2026:50572 - Security Advisory

Topic

An update for mod_http2 is now available for Red Hat Enterprise Linux 9.6 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 9.6 x86_64
• Red Hat Enterprise Linux Server - AUS 9.6 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 9.6 s390x
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 9.6 ppc64le
• Red Hat Enterprise Linux for ARM 64 - Extended Update Support 9.6 aarch64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 9.6 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 9.6 x86_64
• Red Hat Enterprise Linux for ARM 64 - 4 years of updates 9.6 aarch64
• Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 9.6 s390x
• Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 9.6 x86_64
• Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle 9.6 aarch64
• Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle 9.6 ppc64le
• Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle 9.6 s390x

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