Heap-based buffer overflow in Apache HTTP Server - CVE-2026-42536

Vulnerability identifier: #VU133903

CSH Severity: High

CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-42536

CWE-ID: CWE-122

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to heap-based buffer overflow in mod_xml2enc xml2StartParse when parsing untrusted content. A remote attacker can supply crafted content to execute arbitrary code.

Apache HTTP Server
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 15 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 Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
Anolis OS
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Ubuntu
Basesystem Module
Server Applications Module
SUSE Package Hub 15
openSUSE Leap
openEuler
mod_http2
mod_md
apache2 (Ubuntu package)
httpd-tools
httpd-manual
httpd-filesystem
mod_ssl
mod_session
mod_proxy_html
mod_ldap
httpd-devel
httpd
httpd-debuginfo
httpd-debugsource
httpd-help
httpd (Red Hat package)
apache2-doc
apache2-devel
apache2-worker
apache2-tls13-devel
apache2-tls13-debugsource
apache2-tls13-doc
apache2-prefork-debuginfo
apache2
apache2-tls13-prefork-debuginfo
apache2-debuginfo
apache2-tls13-utils-debuginfo
apache2-utils
apache2-tls13-example-pages
apache2-tls13-worker-debuginfo
apache2-debugsource
apache2-example-pages
apache2-tls13-debuginfo
apache2-worker-debuginfo
apache2-tls13-utils
apache2-prefork
apache2-tls13
apache2-utils-debuginfo
apache2-tls13-worker
apache2-tls13-prefork
apache2-event-debuginfo
apache2-event
apache2-worker-debugsource
apache2-prefork-debugsource
apache2-manual
apache2-utils-debugsource
apache2-event-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
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
httpd-tools - update to 2.4.37-655.0.1
httpd-manual - update to 2.4.37-655.0.1
httpd-filesystem - update to 2.4.37-655.0.1
mod_ssl - update to 2.4.37-655.0.1
mod_session - update to 2.4.37-655.0.1
mod_proxy_html - update to 2.4.37-655.0.1
mod_ldap - update to 2.4.37-655.0.1
httpd-devel - update to 2.4.37-655.0.1
httpd - update to 2.4.37-655.0.1
httpd-debuginfo - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
mod_ldap - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
httpd - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
mod_session - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
httpd-debugsource - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
httpd-devel - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
httpd-tools - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
mod_proxy_html - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
httpd-help - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
httpd-filesystem - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
mod_ssl - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
mod_md - addressed in versions 2.4.43-37, 2.4.51-33, 2.4.58-20
httpd (Red Hat package) - addressed in versions 2.4.63-1.el10_0.4, 2.4.63-13.el10_2.4
apache2-doc - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1
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-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-tls13-devel - update to 2.4.66-35.81.1
apache2-tls13-debugsource - update to 2.4.66-35.81.1
apache2-tls13-doc - update to 2.4.66-35.81.1
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 - 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-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-utils-debuginfo - update to 2.4.66-35.81.1
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-example-pages - update to 2.4.66-35.81.1
apache2-tls13-worker-debuginfo - update to 2.4.66-35.81.1
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-example-pages - addressed in versions 2.4.66-35.81.1, 2.4.66-150400.6.57.1
apache2-tls13-debuginfo - 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-tls13-utils - update to 2.4.66-35.81.1
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-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-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-worker-debugsource - 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-manual - 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-event-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
• openEuler 24.03 LTS SP3 update for httpd
• openEuler 24.03 LTS SP1 update for httpd
• openEuler 22.03 LTS SP4 update for httpd
• openEuler 20.03 LTS SP4 update for httpd
• SUSE update for apache2
• Red Hat Enterprise Linux 10 update for httpd
• SUSE update for apache2
• SUSE update for apache2
• 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
• Red Hat Enterprise Linux 10 update for httpd