Description
In certain proxy configurations, a denial of service attack against Apache HTTP Server versions 2.4.26 through to 2.4.63 can be triggered by untrusted clients causing an assertion in mod_proxy_http2.
Configurations affected are a reverse proxy is configured for an HTTP/2 backend, with ProxyPreserveHost set to "on".
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Apache Software Foundation | Apache HTTP Server | 2.4.26 – ≤ 2.4.63 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | apache2 | 2.4.64-1 | — |
| Debian 13 | apache2 | 2.4.64-1 | — |
| Debian 12 | apache2 | 2.4.65-1~deb12u1 | — |
| Debian 11 | apache2 | 2.4.65-1~deb11u1 | DLA-4270-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 24.04 LTS | apache2 | 2.4.58-1ubuntu8.7 | USN-7639-1 |
| Ubuntu 22.04 LTS | apache2 | 2.4.52-1ubuntu4.15 | USN-7639-1 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | apache2 | 2.4.41-4ubuntu3.23+esm2 | USN-7639-2 |
| Ubuntu Pro 18.04 LTS | apache2 | 2.4.29-1ubuntu4.27+esm6 | USN-7639-2 |
| Ubuntu Pro 16.04 LTS | apache2 | 2.4.18-2ubuntu3.17+esm16 | USN-7639-2 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | mod_http2 | 2.0.29-2.el10_0.1 | RHSA-2025:14625 |
| RHEL 9 | mod_http2 | 2.0.26-4.el9_6.1 | RHSA-2025:14983 |
| RHEL 8 | httpd +6 | 2.4.37-65.module+el8.10.0+23369+11a81384.5 | RHSA-2025:15123 |
| RHEL 8 | mod_http2 | 1.15.7-10.module+el8.10.0+23369+11a81384.4 | RHSA-2025:15123 |
| RHEL 8 | mod_md | 1:2.0.8-8.module+el8.9.0+19080+567b90f8 | RHSA-2025:15123 |
| RHEL 8 | mod_ssl +1 | 1:2.4.37-65.module+el8.10.0+23369+11a81384.5 | RHSA-2025:15123 |
Show 11 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9.4 EUS | mod_http2 | 2.0.26-2.el9_4.2 | RHSA-2025:15727 |
| RHEL 9.2 E4S | mod_http2 | 1.15.19-4.el9_2.7 | RHSA-2025:15726 |
| RHEL 9.0 E4S | mod_http2 | 1.15.19-3.el9_0.7 | RHSA-2025:15725 |
| RHEL 8.8 E4S | httpd +6 | 2.4.37-56.module+el8.8.0+23464+a2e0c444.10 | RHSA-2025:15619 |
| RHEL 8.8 E4S | mod_http2 | 1.15.7-8.module+el8.8.0+23464+a2e0c444.6 | RHSA-2025:15619 |
| RHEL 8.8 E4S | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2025:15619 |
| RHEL 8.8 E4S | mod_ssl +1 | 1:2.4.37-56.module+el8.8.0+23464+a2e0c444.10 | RHSA-2025:15619 |
| RHEL 8.6 TUS | httpd +6 | 2.4.37-47.module+el8.6.0+23463+5d5709c6.11 | RHSA-2025:15698 |
| RHEL 8.6 TUS | mod_http2 | 1.15.7-5.module+el8.6.0+23463+5d5709c6.4 | RHSA-2025:15698 |
| RHEL 8.6 TUS | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2025:15698 |
| RHEL 8.6 TUS | mod_ssl +1 | 1:2.4.37-47.module+el8.6.0+23463+5d5709c6.11 | RHSA-2025:15698 |
| RHEL 8.6 E4S | httpd +6 | 2.4.37-47.module+el8.6.0+23463+5d5709c6.11 | RHSA-2025:15698 |
| RHEL 8.6 E4S | mod_http2 | 1.15.7-5.module+el8.6.0+23463+5d5709c6.4 | RHSA-2025:15698 |
| RHEL 8.6 E4S | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2025:15698 |
| RHEL 8.6 E4S | mod_ssl +1 | 1:2.4.37-47.module+el8.6.0+23463+5d5709c6.11 | RHSA-2025:15698 |
| RHEL 8.6 AUS | httpd +6 | 2.4.37-47.module+el8.6.0+23463+5d5709c6.11 | RHSA-2025:15698 |
| RHEL 8.6 AUS | mod_http2 | 1.15.7-5.module+el8.6.0+23463+5d5709c6.4 | RHSA-2025:15698 |
| RHEL 8.6 AUS | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2025:15698 |
| RHEL 8.6 AUS | mod_ssl +1 | 1:2.4.37-47.module+el8.6.0+23463+5d5709c6.11 | RHSA-2025:15698 |
| RHEL 8.4 EUS Long Life | httpd +6 | 2.4.37-39.module+el8.4.0+23462+1fa78ba3.10 | RHSA-2025:15684 |
| RHEL 8.4 EUS Long Life | mod_http2 | 1.15.7-3.module+el8.4.0+23462+1fa78ba3.4 | RHSA-2025:15684 |
| RHEL 8.4 EUS Long Life | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2025:15684 |
| RHEL 8.4 EUS Long Life | mod_ssl +1 | 1:2.4.37-39.module+el8.4.0+23462+1fa78ba3.10 | RHSA-2025:15684 |
| RHEL 8.4 AUS | httpd +6 | 2.4.37-39.module+el8.4.0+23462+1fa78ba3.10 | RHSA-2025:15684 |
| RHEL 8.4 AUS | mod_http2 | 1.15.7-3.module+el8.4.0+23462+1fa78ba3.4 | RHSA-2025:15684 |
| RHEL 8.4 AUS | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2025:15684 |
| RHEL 8.4 AUS | mod_ssl +1 | 1:2.4.37-39.module+el8.4.0+23462+1fa78ba3.10 | RHSA-2025:15684 |
| RHEL 8.2 AUS | httpd +6 | 2.4.37-21.module+el8.2.0+23461+1d03af5c.10 | RHSA-2025:15516 |
| RHEL 8.2 AUS | mod_http2 | 1.11.3-3.module+el8.2.0+23461+1d03af5c.5 | RHSA-2025:15516 |
| RHEL 8.2 AUS | mod_md | 1:2.0.8-7.module+el8.2.0+5531+7e4d69a2 | RHSA-2025:15516 |
| RHEL 8.2 AUS | mod_ssl +1 | 1:2.4.37-21.module+el8.2.0+23461+1d03af5c.10 | RHSA-2025:15516 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-httpd +6 | 2.4.62-8.el7jbcs | RHSA-2025:13680 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_http2 | 2.0.29-5.el7jbcs | RHSA-2025:13680 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_jk +1 | 1.2.50-9.redhat_1.el7jbcs | RHSA-2025:13680 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_md | 1:2.4.28-10.el7jbcs | RHSA-2025:13680 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_proxy_cluster | 1.3.22-4.el7jbcs | RHSA-2025:13680 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_security | 2.9.6-11.el7jbcs | RHSA-2025:13680 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_ssl +1 | 1:2.4.62-8.el7jbcs | RHSA-2025:13680 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | mod_http2 | 2.0.29-2.el10_0.1 | ALSA-2025:14625 |
| AlmaLinux 9 | mod_http2 | 2.0.26-4.el9_6.1 | ALSA-2025:14983 |
| AlmaLinux 8 | httpd +6 | 2.4.37-65.module_el8.10.0+4044+ea5f78b1.5 | ALSA-2025:15123 |
| AlmaLinux 8 | mod_http2 | 1.15.7-10.module_el8.10.0+4044+ea5f78b1.4 | ALSA-2025:15123 |
| AlmaLinux 8 | mod_md | 1:2.0.8-8.module_el8.6.0+2872+fe0ff7aa | ALSA-2025:15123 |
| AlmaLinux 8 | mod_ssl +1 | 1:2.4.37-65.module_el8.10.0+4044+ea5f78b1.5 | ALSA-2025:15123 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | mod_http2 | 2.0.29-2.el10_0.1 | RLSA-2025:14625 |
| Rocky Linux 9 | mod_http2 | 2.0.26-4.el9_6.1 | RLSA-2025:14983 |
| Rocky Linux 8 | httpd | 2.4.37-65.module+el8.10.0+1830+22f0c9e0 | RLSA-2025:15123 |
| Rocky Linux 8 | mod_http2 | 1.15.7-10.module+el8.10.0+1775+6b057638 | RLSA-2025:15123 |
| Rocky Linux 8 | mod_md | 1:2.0.8-8.module+el8.9.0+1370+89cc8ad5 | RLSA-2025:15123 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2025:02685-1, SUSE-SU-2025:02682-1 |
| SLES 15 SP7 | apache2-devel +4 | 2.4.62-150700.4.3.1 | SUSE-SU-2025:02685-1 |
| SLES 15 SP6 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2025:02684-1, SUSE-SU-2025:02682-1 |
| SLES 15 SP6 | apache2-devel +4 | 2.4.58-150600.5.35.1 | SUSE-SU-2025:02684-1 |
| SLES 15 SP5 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2026:2686-1, SUSE-SU-2025:02682-1 |
| SLES 15 SP4 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2026:2686-1, SUSE-SU-2025:02682-1 |
| SLES 15 SP3 | apache2 | 2.4.51-150200.3.82.1 | SUSE-SU-2025:02683-1 |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP5 | apache2 +1 | 2.4.51-35.69.1 | SUSE-SU-2025:02565-1 |
| SLES for SAP 15 SP5 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2026:2686-1, SUSE-SU-2025:02682-1 |
| SLES for SAP 15 SP4 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2026:2686-1, SUSE-SU-2025:02682-1 |
| SLES for SAP 15 SP3 | apache2 | 2.4.51-150200.3.82.1 | SUSE-SU-2025:02683-1 |
| SLE HPC 15 SP5 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2026:2686-1, SUSE-SU-2025:02682-1 |
| SLE HPC 15 SP4 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2026:2686-1, SUSE-SU-2025:02682-1 |
| SLE HPC 15 SP3 | apache2 | 2.4.51-150200.3.82.1 | SUSE-SU-2025:02683-1 |
| SUSE Manager Server 4.3 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2025:02682-1 |
| SUSE Manager Proxy 4.3 | apache2 | 2.4.51-150400.6.46.1 | SUSE-SU-2025:02682-1 |
| SUSE Enterprise Storage 7.1 | apache2 | 2.4.51-150200.3.82.1 | SUSE-SU-2025:02683-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | apache2 | 2.4.64-1.1 | openSUSE-SU-2025:15360-1 |
| openSUSE Leap 15.6 | apache2 +6 | 2.4.58-150600.5.35.1 | SUSE-SU-2025:02684-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | apache2 | 2.4.64-r0 | — |
| Alpine v3.23 | apache2 | 2.4.64-r0 | — |
| Alpine v3.22 | apache2 | 2.4.64-r0 | — |
| Alpine v3.21 | apache2 | 2.4.64-r0 | — |
| Alpine v3.20 | apache2 | 2.4.64-r0 | — |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | apache2 | 2.4.64-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | httpd +8 | 2.4.64-1.amzn2023.0.1 | ALAS2023-2025-1125 |
| Amazon Linux 2023 | mod_ssl +1 | 1:2.4.64-1.amzn2023.0.1 | ALAS2023-2025-1125 |
| Amazon Linux 2 | httpd +7 | 2.4.64-1.amzn2.0.1 | ALAS2-2025-2958 |
| Amazon Linux 2 | mod_ssl +1 | 1:2.4.64-1.amzn2.0.1 | ALAS2-2025-2958 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | httpd | 2.4.64-1 | — |
| Azure Linux 3 | mod_http2 | No fix yet | — |
| Azure Linux 2 (CBL-Mariner) | httpd | 2.4.64-1 | — |
| Azure Linux 2 (CBL-Mariner) | mod_http2 | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | mod_http2 | 2.0.29-2.el10_0.1 | ELSA-2025-14625 |
| Oracle Linux 9 | mod_http2 | 2.0.26-4.el9_6.1 | ELSA-2025-14983 |
| Oracle Linux 8 | httpd +6 | 2.4.37-65.0.1.module+el8.10.0+90652+bef864ba.5 | ELSA-2025-15123 |
| Oracle Linux 8 | mod_http2 | 1.15.7-10.module+el8.10.0+90652+bef864ba.4 | ELSA-2025-15123 |
| Oracle Linux 8 | mod_md | 1:2.0.8-8.module+el8.9.0+90011+2f9c6a23 | ELSA-2025-15123 |
| Oracle Linux 8 | mod_ssl +1 | 1:2.4.37-65.0.1.module+el8.10.0+90652+bef864ba.5 | ELSA-2025-15123 |
Advisories 34
- WID-SEC-2025-1529 Apache HTTP Server: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 11, 2026
- ALSA-2025:14625 Moderate: mod_http2 security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2025:14983 Moderate: mod_http2 security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2025:15123 Moderate: httpd:2.4 security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2025:15698 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- RHSA-2025:15684 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- RHSA-2025:15516 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- RHSA-2025:15619 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- RHSA-2025:15123 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- RHSA-2025:13680 Red Hat Security Advisory: Red Hat JBoss Core Services Apache HTTP Server 2.4.62 SP1 security update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- RHSA-2025:15727 Red Hat Security Advisory: mod_http2 security update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- RHSA-2025:15726 Red Hat Security Advisory: mod_http2 security update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- RHSA-2025:15725 Red Hat Security Advisory: mod_http2 security update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- RHSA-2025:14983 Red Hat Security Advisory: mod_http2 security update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- RHSA-2025:14625 Red Hat Security Advisory: mod_http2 security update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- SUSE-SU-2026:2686-1 Security update for apache2 SUSE / openSUSE Security Updates · Jul 1, 2026
- USN-7639-2 apache2 vulnerabilities Ubuntu Security Notices (USN) · Jun 25, 2026
- USN-7639-1 apache2 vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- openSUSE-SU-2025:15360-1 apache2-2.4.64-1.1 on GA media SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:02683-1 Security update for apache2 SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:02682-1 Security update for apache2 SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:02684-1 Security update for apache2 SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:02685-1 Security update for apache2 SUSE / openSUSE Security Updates · Mar 23, 2026
- DLA-4270-1 apache2 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2025:02565-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2025-1850 Xerox FreeFlow Print Server: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff BSI CERT-Bund (WID) · Nov 17, 2025
- RLSA-2025:14983 Moderate: mod_http2 security update Rocky Linux Security Advisories · Oct 10, 2025
- RLSA-2025:14625 Moderate: mod_http2 security update Rocky Linux Security Advisories · Oct 8, 2025
- RLSA-2025:15123 Moderate: httpd:2.4 security update Rocky Linux Security Advisories · Sep 8, 2025
- ELSA-2025-15123 Moderate: httpd:2.4 security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Sep 4, 2025
- ELSA-2025-14983 Moderate: mod_http2 security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Sep 1, 2025
- ELSA-2025-14625 Moderate: mod_http2 security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Aug 26, 2025
- ALAS2023-2025-1125 Important: httpd security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Aug 8, 2025
- ALAS2-2025-2958 Important: httpd security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Aug 4, 2025
References
- https://httpd.apache.org/security/vulnerabilities_24.html vendor-advisory