Double free in Apache HTTP Server - CVE-2026-23918

Vulnerability identifier: #VU129550

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-2026-23918

CWE-ID: CWE-415

Exploitation vector: Remote access

Exploit availability: Public exploit is available

The vulnerability allows a remote attacker to cause a denial of service and possibly execute arbitrary code.

The vulnerability exists due to a double free in Apache HTTP Server HTTP/2 handling when processing an early reset. A remote attacker can trigger an early reset condition to cause a denial of service and possibly execute arbitrary code.

The issue is specific to the HTTP/2 protocol.

Apache HTTP Server
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 15 SP4
Debian Linux
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Package Hub 15
Server Applications Module
Basesystem Module
openSUSE Leap
Ubuntu
Anolis OS
SecurityCenter
apache2 (Ubuntu package)
apache2-utils
apache2-example-pages
apache2-tls13-utils-debuginfo
apache2-tls13
apache2-tls13-debuginfo
apache2-tls13-debugsource
apache2-tls13-worker
apache2-debuginfo
apache2
apache2-tls13-example-pages
apache2-utils-debuginfo
apache2-tls13-worker-debuginfo
apache2-debugsource
apache2-devel
apache2-tls13-devel
apache2-prefork
apache2-tls13-prefork-debuginfo
apache2-worker
apache2-prefork-debuginfo
apache2-tls13-utils
apache2-worker-debuginfo
apache2-doc
apache2-tls13-doc
apache2-tls13-prefork
apache2-event
apache2-event-debuginfo
apache2-prefork-debugsource
apache2-manual
apache2-event-debugsource
apache2-worker-debugsource
apache2-utils-debugsource
mod_proxy_html
httpd
httpd-core
httpd-devel
httpd-tools
mod_ldap
httpd-manual
httpd-filesystem
httpd-doc
mod_ssl
mod_session
mod_lua
apache2 (Debian package)

Install security update from vendor's website.

Apache HTTP Server - update to 2.4.67
SecurityCenter - addressed in versions SC202607.1, SC202607.2
apache2 (Ubuntu package) - addressed in versions 2.4.52-1ubuntu4.20, 2.4.58-1ubuntu8.12, 2.4.64-1ubuntu3.4, 2.4.66-2ubuntu2.1
apache2-utils - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-example-pages - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1
apache2-tls13-utils-debuginfo - update to 2.4.66-35.78.1
apache2-tls13 - update to 2.4.66-35.78.1
apache2-tls13-debuginfo - update to 2.4.66-35.78.1
apache2-tls13-debugsource - update to 2.4.66-35.78.1
apache2-tls13-worker - update to 2.4.66-35.78.1
apache2-debuginfo - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2 - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-tls13-example-pages - update to 2.4.66-35.78.1
apache2-utils-debuginfo - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-tls13-worker-debuginfo - update to 2.4.66-35.78.1
apache2-debugsource - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-devel - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-tls13-devel - update to 2.4.66-35.78.1
apache2-prefork - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-tls13-prefork-debuginfo - update to 2.4.66-35.78.1
apache2-worker - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-prefork-debuginfo - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-tls13-utils - update to 2.4.66-35.78.1
apache2-worker-debuginfo - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-doc - addressed in versions 2.4.66-35.78.1, 2.4.66-150400.6.57.1
apache2-tls13-doc - update to 2.4.66-35.78.1
apache2-tls13-prefork - update to 2.4.66-35.78.1
apache2-event - addressed in versions 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-event-debuginfo - addressed in versions 2.4.66-150400.6.57.1, 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-prefork-debugsource - addressed in versions 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-manual - addressed in versions 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-event-debugsource - addressed in versions 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-worker-debugsource - addressed in versions 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
apache2-utils-debugsource - addressed in versions 2.4.66-150600.5.52.1, 2.4.66-150700.4.20.1
mod_proxy_html - update to 2.4.67-1
httpd - update to 2.4.67-1
httpd-core - update to 2.4.67-1
httpd-devel - update to 2.4.67-1
httpd-tools - update to 2.4.67-1
mod_ldap - update to 2.4.67-1
httpd-manual - update to 2.4.67-1
httpd-filesystem - update to 2.4.67-1
httpd-doc - update to 2.4.67-1
mod_ssl - update to 2.4.67-1
mod_session - update to 2.4.67-1
mod_lua - update to 2.4.67-1
apache2 (Debian package) - addressed in versions 2.4.67-1~deb12u2, 2.4.67-1~deb13u2

• Exploit #12779 - CVE-2026-23918-Apache-H2-PoC (Proof-of-Concept exploit for CVE-2026-23918 (Apache mod_http2 double-free). Features multi-mode DoS (Rapid-RST, Slow-Drip) and passive RCE/vulnerability detection for Apache 2.4.66.) (June 23, 2026)

• https://httpd.apache.org/security/vulnerabilities_24.html#CVE-2026-23918
• https://lists.apache.org/thread/otwt07gfnp6x2b58hnbghgs9r4ovy3yf

• Multiple vulnerabilities in Apache HTTP Server
• Ubuntu update for apache2
• Debian update for apache2
• SUSE update for apache2
• SUSE update for apache2
• Anolis OS update for httpd
• SUSE update for apache2
• SUSE update for apache2
• Multiple vulnerabilities in Tenable Security Center
• Tenable Security Center on Enclave Security update for third-party components