Description
Possible CRLF injection allowing HTTP response splitting attacks for sites which use mod_userdir. This issue was mitigated by changes made in 2.4.25 and 2.2.32 which prohibit CR or LF injection into the "Location" or other outbound header key or value. Fixed in Apache HTTP Server 2.4.25 (Affected 2.4.1-2.4.23). Fixed in Apache HTTP Server 2.2.32 (Affected 2.2.0-2.2.31).
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Apache Software Foundation | Apache HTTP Server | Fixed in Apache HTTP Server 2.4.25 (Affected 2.4.1-2.4.23), Fixed in Apache HTTP Server 2.2.32 (Affected 2.2.0-2.2.31) | — |
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 | 2.4.25-1 | — |
| Debian 13 | apache2 | 2.4.25-1 | — |
| Debian 12 | apache2 | 2.4.25-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | apache2 | 2.4.18-2ubuntu3.2 | — |
| Ubuntu 14.04 LTS | apache2 | 2.4.7-1ubuntu4.15 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 7 | httpd +5 | 2.4.6-45.el7_3.4 | RHSA-2017:0906 |
| RHEL 7 | mod_ssl +1 | 1:2.4.6-45.el7_3.4 | RHSA-2017:0906 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apache-commons-daemon | 1.1.0-1.redhat_2.1.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apache-commons-daemon-jsvc | 1:1.1.0-1.redhat_2.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apr +1 | 1.6.3-14.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-apr-util +8 | 1.6.1-9.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-httpd +6 | 2.4.29-17.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_auth_kerb | 5.4-36.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_bmx | 0.9.6-17.GA.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_cluster-native | 1.3.8-1.Final_redhat_2.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_jk +2 | 1.2.43-1.redhat_1.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_rt | 2.4.1-19.GA.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_security | 2.9.1-23.GA.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-mod_ssl +1 | 1:2.4.29-17.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-nghttp2 +1 | 1.29.0-8.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
| Red Hat JBoss Core Services 1 | jbcs-httpd24-openssl +4 | 1:1.0.2n-11.jbcs.el6 | RHSA-2018:2186, RHSA-2018:2185 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP3 | apache2 | 2.4.23-29.24.1 | SUSE-SU-2018:2815-1 |
| SLES 12 SP2 | apache2 | 2.4.23-29.24.1 | SUSE-SU-2018:2815-2, SUSE-SU-2018:2815-1 |
| SLES 12 SP1 | apache2 | 2.4.16-20.19.1 | SUSE-SU-2018:2554-1 |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP3 | apache2 | 2.4.23-29.24.1 | SUSE-SU-2018:2815-1 |
| SLES for SAP 12 SP2 | apache2 | 2.4.23-29.24.1 | SUSE-SU-2018:2815-1 |
| SLES for SAP 12 SP1 | apache2 | 2.4.16-20.19.1 | SUSE-SU-2018:2554-1 |
| SUSE OpenStack Cloud 7 | apache2 | 2.4.23-29.24.1 | SUSE-SU-2018:2815-1 |
| SUSE Enterprise Storage 4 | apache2 | 2.4.23-29.24.1 | SUSE-SU-2018:2815-1 |
Automated scanner template
A ready-made Nuclei template detects this vulnerability automatically. Vulnerabilities with public scanner templates are typically probed across the internet soon after the template appears — exposed systems should be patched first.
- Apache mod_userdir CRLF injection http/cves/2016/CVE-2016-4975.yaml
Source: projectdiscovery/nuclei-templates (MIT) — updated daily. Only links are listed.
Advisories 6
- RHSA-2018:2186 Red Hat Security Advisory: Red Hat JBoss Core Services Apache HTTP Server 2.4.29 RHEL 6 security update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- RHSA-2018:2185 Red Hat Security Advisory: Red Hat JBoss Core Services Apache HTTP Server 2.4.29 RHEL 7 security update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- RHSA-2017:0906 Red Hat Security Advisory: httpd security and bug fix update Red Hat Security Advisories (RHSA) · Sep 21, 2026
- SUSE-SU-2018:2815-1 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2018:2815-2 Security update for apache2 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2018:2554-1 Security update for apache2 SUSE / openSUSE Security Updates · May 2, 2025
References
- https://httpd.apache.org/security/vulnerabilities_22.html#CVE-2016-4975
- https://security.netapp.com/advisory/ntap-20180926-0006/
- https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03908en_us
- 105093 vdb-entry
- https://httpd.apache.org/security/vulnerabilities_24.html#CVE-2016-4975
- [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
- [httpd-cvs] 20190815 svn commit: r1048743 [3/4] - 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 [3/4] - 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: r1058586 [3/4] - 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: 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] 20200401 svn commit: r1058587 [3/4] - 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: r1073140 [3/4] - 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: 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: r1888194 [10/13] - /httpd/site/trunk/content/security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073139 [10/13] - in /websites/staging/httpd/trunk/content: ./ security/json/ mailing-list
- [httpd-cvs] 20210330 svn commit: r1073146 [2/3] - in /websites/staging/httpd/trunk/content: ./ security/cvejsontohtml.py security/vulnerabilities-httpd.xml security/vulnerabilities_22.html security/vulnerabilities_24.html 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: r1073146 [3/3] - in /websites/staging/httpd/trunk/content: ./ security/cvejsontohtml.py security/vulnerabilities-httpd.xml security/vulnerabilities_22.html security/vulnerabilities_24.html mailing-list
- [httpd-cvs] 20210330 svn commit: r1073149 [10/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/ mailing-list
- [httpd-cvs] 20210603 svn commit: r1075360 [3/3] - in /websites/staging/httpd/trunk/content: ./ security/json/CVE-2021-31618.json security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabiliti mailing-list
- [httpd-cvs] 20210606 svn commit: r1075470 [3/4] - 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