Description
In Apache HTTP server versions 2.4.37 and prior, by sending request bodies in a slow loris way to plain resources, the h2 stream for that request unnecessarily occupied a server thread cleaning up that incoming data. This affects only HTTP/2 (mod_http2) connections.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Apache Software Foundation | Apache HTTP Server | 2.4.17 to 2.4.37 | — |
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 | 2.4.38-1 | — |
| Debian 13 | apache2 | 2.4.38-1 | — |
| Debian 12 | apache2 | 2.4.38-1 | — |
| Debian 9 | apache2 | 2.4.25-3+deb9u7 | DSA-4422-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | apache2 | 2.4.29-1ubuntu4.6 | USN-3937-1 |
| Ubuntu 16.04 LTS | apache2 | 2.4.18-2ubuntu3.10 | USN-3937-1 |
| Ubuntu 14.04 LTS | apache2 | 2.4.7-1ubuntu4.22 | USN-3937-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | httpd +6 | 2.4.37-30.module+el8.3.0+7001+0766b9e7 | RHSA-2020:4751 |
| RHEL 8 | mod_http2 | 1.15.7-2.module+el8.3.0+7670+8bf57d29 | RHSA-2020:4751 |
| RHEL 8 | mod_md | 1:2.0.8-8.module+el8.3.0+6814+67d1e611 | RHSA-2020:4751 |
| RHEL 8 | mod_ssl +1 | 1:2.4.37-30.module+el8.3.0+7001+0766b9e7 | RHSA-2020:4751 |
| RHEL 3 | httpd24 +3 | 1.1-19.el6 | RHSA-2019:4126 |
| RHEL 3 | httpd24-httpd +5 | 2.4.34-15.el6 | RHSA-2019:4126 |
| RHEL 3 | httpd24-mod_md | 2.4.34-15.el7 | RHSA-2019:4126 |
| RHEL 3 | httpd24-mod_ssl +1 | 1:2.4.34-15.el6 | RHSA-2019:4126 |
| RHEL 3 | httpd24-nghttp2 +2 | 1.7.1-8.el6 | RHSA-2019:4126 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apr +1 | 1.6.3-63.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apr-util +8 | 1.6.1-48.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-brotli +1 | 1.0.6-7.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-curl +2 | 7.64.1-14.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-httpd +7 | 2.4.37-33.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-jansson +1 | 2.11-20.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_cluster-native | 1.3.12-9.Final_redhat_2.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_jk +2 | 1.2.46-22.redhat_1.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_security | 2.9.2-16.GA.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_ssl +1 | 1:2.4.37-33.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-nghttp2 +1 | 1.39.2-4.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl +4 | 1:1.1.1-25.jbcs.el6 | RHSA-2019:3933, RHSA-2019:3932 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | mod_md | 1:2.0.8-8.module_el8.5.0+2609+b30d9eec | ALSA-2020:4751 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | mod_md | 1:2.0.8-8.module+el8.4.0+553+7a69454b | RLSA-2020:4751 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 | apache2 | 2.4.33-3.9.7 | SUSE-SU-2019:0504-1 |
| SLES 12 SP4 | apache2 | 2.4.23-29.34.4 | SUSE-SU-2019:0498-1 |
| SLES 12 SP3 | apache2 | 2.4.23-29.34.4 | SUSE-SU-2019:0498-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP4 | apache2 | 2.4.23-29.34.4 | SUSE-SU-2019:0498-1 |
| SLES for SAP 12 SP3 | apache2 | 2.4.23-29.34.4 | SUSE-SU-2019:0498-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 15.0 | apache2 | 2.4.33-lp150.2.9.1 | openSUSE-SU-2019:0296-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | apache2 | 2.4.38-r0 | — |
| Alpine v3.23 | apache2 | 2.4.38-r0 | — |
| Alpine v3.22 | apache2 | 2.4.38-r0 | — |
| Alpine v3.21 | apache2 | 2.4.38-r0 | — |
| Alpine v3.20 | apache2 | 2.4.38-r0 | — |
Show 14 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | apache2 | 2.4.38-r0 | — |
| Alpine v3.18 | apache2 | 2.4.38-r0 | — |
| Alpine v3.17 | apache2 | 2.4.38-r0 | — |
| Alpine v3.16 | apache2 | 2.4.38-r0 | — |
| Alpine v3.15 | apache2 | 2.4.38-r0 | — |
| Alpine v3.14 | apache2 | 2.4.38-r0 | — |
| Alpine v3.13 | apache2 | 2.4.38-r0 | — |
| Alpine v3.12 | apache2 | 2.4.38-r0 | — |
| Alpine v3.11 | apache2 | 2.4.38-r0 | — |
| Alpine v3.10 | apache2 | 2.4.38-r0 | — |
| Alpine v3.9 | apache2 | 2.4.38-r0 | — |
| Alpine v3.8 | apache2 | 2.4.38-r0 | — |
| Alpine v3.7 | apache2 | 2.4.38-r0 | — |
| Alpine v3.6 | apache2 | 2.4.38-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | mod_http2 | 1.14.1-1.amzn2 | ALAS2-2019-1197 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | httpd +6 | 2.4.37-30.0.1.module+el8.3.0+7816+49791cfd | ELSA-2020-4751 |
| Oracle Linux 8 | mod_http2 | 1.15.7-2.module+el8.3.0+7816+49791cfd | ELSA-2020-4751 |
| Oracle Linux 8 | mod_md | 1:2.0.8-8.module+el8.3.0+7816+49791cfd | ELSA-2020-4751 |
| Oracle Linux 8 | mod_ssl +1 | 1:2.4.37-30.0.1.module+el8.3.0+7816+49791cfd | ELSA-2020-4751 |
Advisories 13
- ALSA-2020:4751 Moderate: httpd:2.4 security, bug fix, and enhancement update AlmaLinux Security Advisories · Nov 2, 2026
- RHSA-2019:3933 Red Hat Security Advisory: Red Hat JBoss Core Services Apache HTTP Server 2.4.37 Security Release on RHEL 7 Red Hat Security Advisories (RHSA) · Oct 16, 2026
- RHSA-2019:3932 Red Hat Security Advisory: Red Hat JBoss Core Services Apache HTTP Server 2.4.37 Security Release on RHEL 6 Red Hat Security Advisories (RHSA) · Oct 16, 2026
- RHSA-2020:4751 Red Hat Security Advisory: httpd:2.4 security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- RHSA-2019:4126 Red Hat Security Advisory: httpd24-httpd security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- USN-3937-1 apache2 vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- DSA-4422-1 apache2 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2020:4751 Moderate: httpd:2.4 security, bug fix, and enhancement update Rocky Linux Security Advisories · Feb 5, 2026
- SUSE-SU-2019:0498-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2019:0296-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:0504-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- ELSA-2020-4751 Moderate: httpd:2.4 security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 10, 2020
- ALAS2-2019-1197 Low: mod_http2 security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Apr 26, 2019
References
- https://httpd.apache.org/security/vulnerabilities_24.html
- 106685 vdb-entry
- https://security.netapp.com/advisory/ntap-20190125-0001/
- FEDORA-2019-0300c36537 vendor-advisory
- FEDORA-2019-133a8a7cb5 vendor-advisory
- GLSA-201903-21 vendor-advisory
- 20190403 [SECURITY] [DSA 4422-1] apache2 security update mailing-list
- USN-3937-1 vendor-advisory
- DSA-4422 vendor-advisory
- https://www.oracle.com/technetwork/security-advisory/cpuapr2019-5072813.html
- https://www.oracle.com/technetwork/security-advisory/cpujul2019-5072835.html
- [httpd-cvs] 20190815 svn commit: r1048743 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilit mailing-list
- [httpd-cvs] 20190815 svn commit: r1048742 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilit mailing-list
- https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03950en_us
- RHSA-2019:3933 vendor-advisory
- RHSA-2019:3935 vendor-advisory
- RHSA-2019:3932 vendor-advisory
- RHSA-2019:4126 vendor-advisory
- https://www.tenable.com/security/tns-2019-09
- https://www.oracle.com/security-alerts/cpujan2020.html
- [httpd-cvs] 20200401 svn commit: r1058586 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilit mailing-list
- [httpd-cvs] 20200401 svn commit: r1058587 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilit mailing-list
- [httpd-cvs] 20210330 svn commit: r1073139 [1/13] - in /websites/staging/httpd/trunk/content: ./ security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073143 [3/3] - in /websites/staging/httpd/trunk/content: ./ security/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073140 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/cvejsontohtml.py security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.ht mailing-list
- [httpd-cvs] 20210330 svn commit: r1073139 [11/13] - in /websites/staging/httpd/trunk/content: ./ security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1888194 [12/13] - /httpd/site/trunk/content/security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073149 [1/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073149 [12/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/ mailing-list
- [httpd-cvs] 20210606 svn commit: r1075470 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/json/CVE-2020-13938.json security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabiliti mailing-list