Out-of-bounds read in Apache HTTP Server - CVE-2026-43951

Vulnerability identifier: #VU133902

CSH Severity: Medium

CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-43951

CWE-ID: CWE-125

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to out-of-bounds read in merge_response_headers when processing responses with mod_headers, mod_mime, and multiple response languages. A remote attacker can trigger processing of affected responses to cause a denial of service.

The issue occurs when mod_headers and mod_mime are used with multiple response languages.

Apache HTTP Server
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
Red Hat Enterprise Linux for ARM 64
Anolis OS
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Ubuntu
Basesystem Module
Server Applications Module
SUSE Package Hub 15
openSUSE Leap
openEuler
WebSphere Remote Server
IBM Rational ClearQuest
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
mod_http2
mod_md
http2 (Red Hat package)
apache2 (Ubuntu package)
mod_ssl
httpd
httpd-devel
httpd-tools
httpd-manual
mod_ldap
httpd-filesystem
mod_proxy_html
mod_session
httpd-debuginfo
httpd-debugsource
httpd-help
apache2-tls13-debuginfo
apache2-tls13-devel
apache2-worker
apache2-devel
apache2-tls13-debugsource
apache2-tls13-example-pages
apache2-tls13-worker-debuginfo
apache2-example-pages
apache2-tls13-utils-debuginfo
apache2-debuginfo
apache2-tls13-prefork-debuginfo
apache2
apache2-prefork-debuginfo
apache2-tls13-doc
apache2-doc
apache2-debugsource
apache2-prefork
apache2-utils
apache2-tls13
apache2-utils-debuginfo
apache2-tls13-worker
apache2-tls13-prefork
apache2-tls13-utils
apache2-worker-debuginfo
apache2-event-debuginfo
apache2-event
apache2-event-debugsource
apache2-utils-debugsource
apache2-manual
apache2-prefork-debugsource
apache2-worker-debugsource

Install security update from vendor's website.

Apache HTTP Server - update to 2.4.68
mod_http2 - update to 1.15.7-10
mod_md - update to 2.0.8-8
http2 (Red Hat package) - addressed in versions 2.0.26-4.el9_6.2, 2.0.29-2.el10_0.2, 2.0.29-4.el10_2.2
apache2 (Ubuntu package) - addressed in versions 2.4.7-1ubuntu4.22+esm14, 2.4.18-2ubuntu3.17+esm19, 2.4.29-1ubuntu4.27+esm10, 2.4.41-4ubuntu3.23+esm5, 2.4.52-1ubuntu4.23, 2.4.58-1ubuntu8.15, 2.4.66-2ubuntu2.4
mod_ssl - update to 2.4.37-655.0.1
httpd - update to 2.4.37-655.0.1
httpd-devel - update to 2.4.37-655.0.1
httpd-tools - update to 2.4.37-655.0.1
httpd-manual - update to 2.4.37-655.0.1
mod_ldap - update to 2.4.37-655.0.1
httpd-filesystem - update to 2.4.37-655.0.1
mod_proxy_html - update to 2.4.37-655.0.1
mod_session - update to 2.4.37-655.0.1
httpd - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
httpd-debuginfo - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
httpd-debugsource - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
httpd-devel - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
httpd-tools - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
mod_ldap - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
mod_md - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
mod_session - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
mod_ssl - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
httpd-filesystem - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
httpd-help - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
mod_proxy_html - addressed in versions 2.4.43-39, 2.4.51-34, 2.4.58-20
apache2-tls13-debuginfo - update to 2.4.66-35.81.1
apache2-tls13-devel - update to 2.4.66-35.81.1
apache2-worker - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-devel - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-tls13-debugsource - update to 2.4.66-35.81.1
apache2-tls13-example-pages - update to 2.4.66-35.81.1
apache2-tls13-worker-debuginfo - update to 2.4.66-35.81.1
apache2-example-pages - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1
apache2-tls13-utils-debuginfo - update to 2.4.66-35.81.1
apache2-debuginfo - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-tls13-prefork-debuginfo - update to 2.4.66-35.81.1
apache2 - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-prefork-debuginfo - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-tls13-doc - update to 2.4.66-35.81.1
apache2-doc - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1
apache2-debugsource - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-prefork - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-utils - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-tls13 - update to 2.4.66-35.81.1
apache2-utils-debuginfo - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-tls13-worker - update to 2.4.66-35.81.1
apache2-tls13-prefork - update to 2.4.66-35.81.1
apache2-tls13-utils - update to 2.4.66-35.81.1
apache2-worker-debuginfo - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-event-debuginfo - addressed in versions 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-event - addressed in versions 2.4.66-150400.6.57.1, 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-event-debugsource - addressed in versions 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-utils-debugsource - addressed in versions 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-manual - addressed in versions 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-prefork-debugsource - addressed in versions 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1
apache2-worker-debugsource - addressed in versions 2.4.66-150600.5.55.1, 2.4.66-150700.4.23.1

• https://downloads.apache.org/httpd/CHANGES_2.4_2.4.68

• Multiple vulnerabilities in Apache HTTP Server
• Multiple vulnerabilities in IBM WebSphere Remote Server
• openEuler 24.03 LTS SP3 update for httpd
• openEuler 24.03 LTS SP1 update for httpd
• SUSE update for apache2
• SUSE update for apache2
• Red Hat Enterprise Linux 10 update for mod_http2
• SUSE update for apache2
• openEuler 22.03 LTS SP4 update for httpd
• openEuler 20.03 LTS SP4 update for httpd
• SUSE update for apache2
• Ubuntu update for apache2
• Ubuntu update for apache2
• Red Hat Enterprise Linux 8 update for the httpd:2.4 module
• Anolis OS update for httpd:2.4 module
• Multiple vulnerabilities in IBM Rational ClearQuest
• Red Hat Enterprise Linux 10 update for mod_http2
• Red Hat Enterprise Linux 9 update for mod_http2