Description
An integer overflow in the case of failed ACME certificate renewal leads, after a number of failures (~30 days in default configurations), to the backoff timer becoming 0. Attempts to renew the certificate then are repeated without delays until it succeeds.
This issue affects Apache HTTP Server: from 2.4.30 before 2.4.66.
Users are recommended to upgrade to version 2.4.66, which fixes the issue.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Apache Software Foundation | Apache HTTP Server | 2.4.30 – < 2.4.66 | 2.4.66 |
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 | 2.4.66-1 | — |
| Debian 13 | apache2 | 2.4.66-1~deb13u1 | — |
| Debian 12 | apache2 | 2.4.66-1~deb12u1 | — |
| Debian 11 | apache2 | 2.4.66-1~deb11u1 | DLA-4452-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | apache2 | 2.4.66-2ubuntu1 | — |
| Ubuntu 25.10 | apache2 | 2.4.64-1ubuntu3.2 | USN-7968-1 |
| Ubuntu 24.04 LTS | apache2 | 2.4.58-1ubuntu8.10 | USN-7968-1 |
| Ubuntu 22.04 LTS | apache2 | 2.4.52-1ubuntu4.18 | USN-7968-1 |
Show 4 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+esm3 | USN-8338-1 |
| Ubuntu Pro 18.04 LTS | apache2 | 2.4.29-1ubuntu4.27+esm7 | USN-8338-1 |
| Ubuntu Pro 16.04 LTS | apache2 | 2.4.18-2ubuntu3.17+esm17 | USN-8338-1 |
| Ubuntu Pro 14.04 LTS | apache2 | 2.4.7-1ubuntu4.22+esm12 | USN-8338-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | mod_md | 1:2.4.26-4.el10_1 | RHSA-2025:23738 |
| RHEL 9 | mod_md | 1:2.4.26-1.el9_7.1 | RHSA-2025:23739 |
| RHEL 8 | httpd +6 | 2.4.37-65.module+el8.10.0+23815+1b5e1c66.7 | RHSA-2025:23732 |
| RHEL 8 | mod_http2 | 1.15.7-10.module+el8.10.0+23369+11a81384.4 | RHSA-2025:23732 |
| RHEL 8 | mod_md | 1:2.0.8-8.module+el8.10.0+23815+1b5e1c66.2 | RHSA-2025:23732 |
| RHEL 8 | mod_ssl +1 | 1:2.4.37-65.module+el8.10.0+23815+1b5e1c66.7 | RHSA-2025:23732 |
Show 14 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10.0 EUS | mod_md | 1:2.4.26-3.el10_0.1 | RHSA-2026:0093 |
| RHEL 9.6 EUS | mod_md | 1:2.4.26-1.el9_6.1 | RHSA-2026:0094 |
| RHEL 9.4 EUS | mod_md | 1:2.4.19-1.el9_4.1 | RHSA-2026:0029 |
| RHEL 9.2 E4S | mod_md | 1:2.4.19-1.el9_2.1 | RHSA-2026:0030 |
| RHEL 9.0 E4S | mod_md | 1:2.4.0-3.el9_0.1 | RHSA-2026:0092 |
| RHEL 8.8 TUS | httpd +6 | 2.4.37-56.module+el8.8.0+23840+d7e7db80.11 | RHSA-2026:0012 |
| RHEL 8.8 TUS | mod_http2 | 1.15.7-8.module+el8.8.0+23464+a2e0c444.6 | RHSA-2026:0012 |
| RHEL 8.8 TUS | mod_md | 1:2.0.8-8.module+el8.8.0+23840+d7e7db80.1 | RHSA-2026:0012 |
| RHEL 8.8 TUS | mod_ssl +1 | 1:2.4.37-56.module+el8.8.0+23840+d7e7db80.11 | RHSA-2026:0012 |
| RHEL 8.8 E4S | httpd +6 | 2.4.37-56.module+el8.8.0+23840+d7e7db80.11 | RHSA-2026:0012 |
| RHEL 8.8 E4S | mod_http2 | 1.15.7-8.module+el8.8.0+23464+a2e0c444.6 | RHSA-2026:0012 |
| RHEL 8.8 E4S | mod_md | 1:2.0.8-8.module+el8.8.0+23840+d7e7db80.1 | RHSA-2026:0012 |
| RHEL 8.8 E4S | mod_ssl +1 | 1:2.4.37-56.module+el8.8.0+23840+d7e7db80.11 | RHSA-2026:0012 |
| RHEL 8.6 TUS | httpd +6 | 2.4.37-47.module+el8.6.0+23843+c27a5dc4.12 | RHSA-2026:0011 |
| RHEL 8.6 TUS | mod_http2 | 1.15.7-5.module+el8.6.0+23463+5d5709c6.4 | RHSA-2026:0011 |
| RHEL 8.6 TUS | mod_md | 1:2.0.8-8.module+el8.6.0+23843+c27a5dc4.1 | RHSA-2026:0011 |
| RHEL 8.6 TUS | mod_ssl +1 | 1:2.4.37-47.module+el8.6.0+23843+c27a5dc4.12 | RHSA-2026:0011 |
| RHEL 8.6 E4S | httpd +6 | 2.4.37-47.module+el8.6.0+23843+c27a5dc4.12 | RHSA-2026:0011 |
| RHEL 8.6 E4S | mod_http2 | 1.15.7-5.module+el8.6.0+23463+5d5709c6.4 | RHSA-2026:0011 |
| RHEL 8.6 E4S | mod_md | 1:2.0.8-8.module+el8.6.0+23843+c27a5dc4.1 | RHSA-2026:0011 |
| RHEL 8.6 E4S | mod_ssl +1 | 1:2.4.37-47.module+el8.6.0+23843+c27a5dc4.12 | RHSA-2026:0011 |
| RHEL 8.6 AUS | httpd +6 | 2.4.37-47.module+el8.6.0+23843+c27a5dc4.12 | RHSA-2026:0011 |
| RHEL 8.6 AUS | mod_http2 | 1.15.7-5.module+el8.6.0+23463+5d5709c6.4 | RHSA-2026:0011 |
| RHEL 8.6 AUS | mod_md | 1:2.0.8-8.module+el8.6.0+23843+c27a5dc4.1 | RHSA-2026:0011 |
| RHEL 8.6 AUS | mod_ssl +1 | 1:2.4.37-47.module+el8.6.0+23843+c27a5dc4.12 | RHSA-2026:0011 |
| RHEL 8.4 EUS Long Life | httpd +6 | 2.4.37-39.module+el8.4.0+23842+00253415.11 | RHSA-2026:0010 |
| RHEL 8.4 EUS Long Life | mod_http2 | 1.15.7-3.module+el8.4.0+23462+1fa78ba3.4 | RHSA-2026:0010 |
| RHEL 8.4 EUS Long Life | mod_md | 1:2.0.8-8.module+el8.4.0+23842+00253415.1 | RHSA-2026:0010 |
| RHEL 8.4 EUS Long Life | mod_ssl +1 | 1:2.4.37-39.module+el8.4.0+23842+00253415.11 | RHSA-2026:0010 |
| RHEL 8.4 AUS | httpd +6 | 2.4.37-39.module+el8.4.0+23842+00253415.11 | RHSA-2026:0010 |
| RHEL 8.4 AUS | mod_http2 | 1.15.7-3.module+el8.4.0+23462+1fa78ba3.4 | RHSA-2026:0010 |
| RHEL 8.4 AUS | mod_md | 1:2.0.8-8.module+el8.4.0+23842+00253415.1 | RHSA-2026:0010 |
| RHEL 8.4 AUS | mod_ssl +1 | 1:2.4.37-39.module+el8.4.0+23842+00253415.11 | RHSA-2026:0010 |
| RHEL 8.2 AUS | httpd +6 | 2.4.37-21.module+el8.2.0+23841+60fa4803.11 | RHSA-2026:0009 |
| RHEL 8.2 AUS | mod_http2 | 1.11.3-3.module+el8.2.0+23461+1d03af5c.5 | RHSA-2026:0009 |
| RHEL 8.2 AUS | mod_md | 1:2.0.8-7.module+el8.2.0+23841+60fa4803.1 | RHSA-2026:0009 |
| RHEL 8.2 AUS | mod_ssl +1 | 1:2.4.37-21.module+el8.2.0+23841+60fa4803.11 | RHSA-2026:0009 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apr-util +8 | 1.6.3-4.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-curl +2 | 8.11.0-4.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-httpd +6 | 2.4.62-11.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_http2 | 2.0.29-8.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_jk +1 | 1.2.50-12.redhat_1.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_md | 1:2.4.28-13.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_proxy_cluster | 1.3.22-7.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_security | 2.9.6-14.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_ssl +1 | 1:2.4.62-11.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl +4 | 1:1.1.1k-21.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl-chil | 1.0.0-25.el7jbcs | RHSA-2026:2994 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl-pkcs11 | 0.4.12-5.el7jbcs | RHSA-2026:2994 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | mod_md | 1:2.4.26-4.el10_1 | ALSA-2025:23738 |
| AlmaLinux 9 | mod_md | 1:2.4.26-1.el9_7.1 | ALSA-2025:23739 |
| AlmaLinux 8 | httpd +6 | 2.4.37-65.module_el8.10.0+4088+57f011c1.7 | ALSA-2025:23732 |
| AlmaLinux 8 | mod_http2 | 1.15.7-10.module_el8.10.0+4044+ea5f78b1.4 | ALSA-2025:23732 |
| AlmaLinux 8 | mod_md | 1:2.0.8-8.module_el8.10.0+4088+57f011c1.2 | ALSA-2025:23732 |
| AlmaLinux 8 | mod_ssl +1 | 1:2.4.37-65.module_el8.10.0+4088+57f011c1.7 | ALSA-2025:23732 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | mod_md | 1:2.4.26-4.el10_1 | RLSA-2025:23738 |
| Rocky Linux 9 | mod_md | 1:2.4.26-1.el9_7.1 | RLSA-2025:23739 |
| Rocky Linux 8 | httpd | 2.4.37-65.module+el8.10.0+1830+22f0c9e0 | RLSA-2025:23732 |
| Rocky Linux 8 | mod_http2 | 1.15.7-10.module+el8.10.0+1775+6b057638 | RLSA-2025:23732 |
| Rocky Linux 8 | mod_md | 1:2.0.8-8.module+el8.9.0+1370+89cc8ad5 | RLSA-2025:23732 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:0019-1, SUSE-SU-2025:4518-1 |
| SLES 15 SP7 | apache2-devel +4 | 2.4.62-150700.4.9.1 | SUSE-SU-2025:4518-1 |
| SLES 15 SP6 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:0020-1, SUSE-SU-2026:0019-1 |
| SLES 15 SP6 | apache2-devel +3 | 2.4.58-150600.5.41.1 | SUSE-SU-2026:0020-1 |
| SLES 15 SP5 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:2686-1, SUSE-SU-2026:0019-1 |
| SLES 15 SP4 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:2686-1, SUSE-SU-2026:0019-1 |
| SLES 12 SP5 | apache2 +1 | 2.4.51-35.75.1 | SUSE-SU-2025:4488-1 |
Show 9 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | apache2 +6 | 2.4.63-160000.3.1 | SUSE-SU-2026:20081-1 |
| SLES for SAP 15 SP6 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:0020-1, SUSE-SU-2026:0019-1 |
| SLES for SAP 15 SP6 | apache2-devel +3 | 2.4.58-150600.5.41.1 | SUSE-SU-2026:0020-1 |
| SLES for SAP 15 SP5 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:2686-1, SUSE-SU-2026:0019-1 |
| SLES for SAP 15 SP4 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:2686-1, SUSE-SU-2026:0019-1 |
| SLES 16.0 | apache2 +6 | 2.4.63-160000.3.1 | SUSE-SU-2026:20081-1 |
| SLE HPC 15 SP5 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:2686-1, SUSE-SU-2026:0019-1 |
| SLE HPC 15 SP4 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:2686-1, SUSE-SU-2026:0019-1 |
| SUSE Manager Server LTS 4.3 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:0019-1 |
| SUSE Manager Proxy LTS 4.3 | apache2 | 2.4.51-150400.6.52.1 | SUSE-SU-2026:0019-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | apache2 | 2.4.66-1.1 | openSUSE-SU-2025:15808-1 |
| openSUSE Leap 16.0 | apache2 +6 | 2.4.63-160000.3.1 | openSUSE-SU-2026:20030-1 |
| openSUSE Leap 15.6 | apache2 +6 | 2.4.58-150600.5.41.1 | SUSE-SU-2026:0020-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | apache2 | 2.4.66-r0 | — |
| Alpine v3.23 | apache2 | 2.4.66-r0 | — |
| Alpine v3.22 | apache2 | 2.4.66-r0 | — |
| Alpine v3.21 | apache2 | 2.4.66-r0 | — |
| Alpine v3.20 | apache2 | 2.4.66-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | httpd +7 | 2.4.66-1.amzn2.0.1 | ALAS2-2025-3099 |
| Amazon Linux 2 | mod_ssl +1 | 1:2.4.66-1.amzn2.0.1 | ALAS2-2025-3099 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | httpd | 2.4.66-1 | — |
| Azure Linux 3 | mod_md | No fix yet | — |
| Azure Linux 2 (CBL-Mariner) | httpd | 2.4.66-1 | — |
| Azure Linux 2 (CBL-Mariner) | mod_md | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | mod_md | 1:2.4.26-4.el10_1 | ELSA-2025-23738 |
| Oracle Linux 9 | mod_md | 1:2.4.26-1.el9_7.1 | ELSA-2025-23739 |
| Oracle Linux 8 | httpd +6 | 2.4.37-65.0.1.module+el8.10.0+90740+3332f30e.7 | ELSA-2025-23732 |
| Oracle Linux 8 | mod_http2 | 1.15.7-10.module+el8.10.0+90652+bef864ba.4 | ELSA-2025-23732 |
| Oracle Linux 8 | mod_md | 1:2.0.8-8.module+el8.10.0+90740+3332f30e.2 | ELSA-2025-23732 |
| Oracle Linux 8 | mod_ssl +1 | 1:2.4.37-65.0.1.module+el8.10.0+90740+3332f30e.7 | ELSA-2025-23732 |
Advisories 40
- WID-SEC-2026-2189 Dell PowerProtect Data Domain: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 2, 2026
- WID-SEC-2025-2750 Apache HTTP Server: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 1, 2026
- ALSA-2025:23738 Important: mod_md security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2025:23739 Important: mod_md security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2025:23732 Important: httpd:2.4 security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2026:2994 Red Hat Security Advisory: Red Hat JBoss Core Services Apache HTTP Server 2.4.62 SP3 security update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- RHSA-2026:0012 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 16, 2026
- RHSA-2026:0010 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 16, 2026
- RHSA-2026:0011 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 16, 2026
- RHSA-2026:0009 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 16, 2026
- RHSA-2025:23732 Red Hat Security Advisory: httpd:2.4 security update Red Hat Security Advisories (RHSA) · Oct 16, 2026
- RHSA-2026:0094 Red Hat Security Advisory: mod_md security update Red Hat Security Advisories (RHSA) · Sep 19, 2026
- RHSA-2026:0092 Red Hat Security Advisory: mod_md security update Red Hat Security Advisories (RHSA) · Sep 19, 2026
- RHSA-2026:0093 Red Hat Security Advisory: mod_md security update Red Hat Security Advisories (RHSA) · Sep 19, 2026
- RHSA-2026:0029 Red Hat Security Advisory: mod_md security update Red Hat Security Advisories (RHSA) · Sep 19, 2026
- RHSA-2026:0030 Red Hat Security Advisory: mod_md security update Red Hat Security Advisories (RHSA) · Sep 19, 2026
- RHSA-2025:23739 Red Hat Security Advisory: mod_md security update Red Hat Security Advisories (RHSA) · Sep 19, 2026
- RHSA-2025:23738 Red Hat Security Advisory: mod_md security update Red Hat Security Advisories (RHSA) · Sep 19, 2026
- WID-SEC-2026-0349 Dell Avamar und NetWorker: Mehrere Schwachstellen BSI CERT-Bund (WID) · Sep 17, 2026
- WID-SEC-2026-0853 Apple macOS: Mehrere Schwachstellen BSI CERT-Bund (WID) · Sep 8, 2026
- WID-SEC-2026-1730 Xerox FreeFlow Print Server: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff BSI CERT-Bund (WID) · Jul 16, 2026
- SUSE-SU-2026:2686-1 Security update for apache2 SUSE / openSUSE Security Updates · Jul 1, 2026
- USN-8338-1 apache2 vulnerabilities Ubuntu Security Notices (USN) · May 29, 2026
- USN-7968-1 apache2 vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- NCSC-2026-0102 Kwetsbaarheden verholpen in Apple macOS NCSC-NL (Netherlands) · Mar 25, 2026
- openSUSE-SU-2026:20030-1 Security update for apache2 SUSE / openSUSE Security Updates · Mar 23, 2026
- openSUSE-SU-2025:15808-1 apache2-2.4.66-1.1 on GA media SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2026:20081-1 Security update for apache2 SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2026:0019-1 Security update for apache2 SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2026:0020-1 Security update for apache2 SUSE / openSUSE Security Updates · Mar 23, 2026
- DLA-4452-1 apache2 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2025:4518-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:4488-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- ALAS2-2025-3099 Important: httpd security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Jan 5, 2026
- RLSA-2025:23738 Important: mod_md security update Rocky Linux Security Advisories · Dec 24, 2025
- ELSA-2025-23732 Important: httpd:2.4 security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Dec 24, 2025
- RLSA-2025:23739 Important: mod_md security update Rocky Linux Security Advisories · Dec 23, 2025
- RLSA-2025:23732 Important: httpd:2.4 security update Rocky Linux Security Advisories · Dec 22, 2025
- ELSA-2025-23738 Important: mod_md security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Dec 21, 2025
- ELSA-2025-23739 Important: mod_md security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Dec 21, 2025
References
- https://httpd.apache.org/security/vulnerabilities_24.html vendor-advisory