Skip to content
Fencer Intel
medium 6.1

CVE-2016-4975 json

mod_userdir CRLF injection

published 2018-08-14 8 y ago modified 2026-06-17 4 mo ago also EUVD-2016-5946

cvss
6.1
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
19.9%
EPSS 19.9% chance of exploitation in 30 days, percentile 97%
public exploits
0
none known, plus a Nuclei check

Summary

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).

Patch / fix

  • apache2 Debian 14, Debian 13, Debian 12 2.4.25-1

debian advisories DEBIAN-CVE-2016-4975

  • apache2 Ubuntu 14.04 LTS 2.4.7-1ubuntu4.15
  • apache2 Ubuntu 16.04 LTS 2.4.18-2ubuntu3.2

ubuntu advisories UBUNTU-CVE-2016-4975

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • jbcs-httpd24-apr jboss core services 1 1.6.3-14.jbcs.el7
  • jbcs-httpd24-httpd jboss core services 1 2.4.29-17.jbcs.el7
  • jbcs-httpd24-mod_jk jboss core services 1 1.2.43-1.redhat_1.jbcs.el7
  • jbcs-httpd24-mod_rt jboss core services 1 2.4.1-19.GA.jbcs.el7
  • jbcs-httpd24-mod_bmx jboss core services 1 0.9.6-17.GA.jbcs.el7
  • jbcs-httpd24-mod_ssl jboss core services 1 1:2.4.29-17.jbcs.el7
  • jbcs-httpd24-nghttp2 jboss core services 1 1.29.0-8.jbcs.el7
  • jbcs-httpd24-openssl jboss core services 1 1:1.0.2n-11.jbcs.el7

red hat advisories RHSA-2018:2185RHSA-2018:2186RHSA-2017:0906

  • apache2 SLES 12 SP3, SLES 12 SP2-BCL, SLE Software Development Kit 12 SP3 +5 more 2.4.23-29.24.1
  • apache2 SLES for SAP 12 SP1, SLES 12 SP1-LTSS 2.4.16-20.19.1

suse advisories SUSE-SU-2018:2815-2SUSE-SU-2018:2815-1SUSE-SU-2018:2554-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-4975 updated cvss 3.7

httpd: CRLF injection allowing HTTP response splitting attacks for sites which use mod_userdir

  • Red Hat Enterprise Linux 5 httpd Red Hat Enterprise Linux 6 httpd, mod_ssl, httpd-tools, httpd-manual
    affected: no fix planned “Will not fix”
  • Red Hat JBoss Enterprise Application Platform 6 httpd, mod_ssl, mod_ldap, httpd-tools, httpd-manual
    affected: no fix available
  • Red Hat JBoss Enterprise Web Server 2 jbcs-httpd24, jbcs-httpd24-runtime
    affected: no fix planned “Will not fix”
  • Red Hat JBoss Enterprise Web Server 3 httpd
    affected: no fix planned “Out of support scope”
  • Red Hat JBoss Web Server 3 httpd24
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux Client Optional (v. 7) httpd 2.4.6-45.el7_3.4, mod_ssl 2.4.6-45.el7_3.4, mod_ldap 2.4.6-45.el7_3.4, httpd-tools 2.4.6-45.el7_3.4, mod_session 2.4.6-45.el7_3.4, httpd-manual 2.4.6-45.el7_3.4, +1 more Red Hat Enterprise Linux ComputeNode Optional (v. 7) httpd 2.4.6-45.el7_3.4, mod_ssl 2.4.6-45.el7_3.4, mod_ldap 2.4.6-45.el7_3.4, httpd-tools 2.4.6-45.el7_3.4, mod_session 2.4.6-45.el7_3.4, httpd-manual 2.4.6-45.el7_3.4, +1 more Red Hat Enterprise Linux Server (v. 7) httpd 2.4.6-45.el7_3.4, mod_ssl 2.4.6-45.el7_3.4, httpd-tools 2.4.6-45.el7_3.4, httpd-manual 2.4.6-45.el7_3.4 Red Hat Enterprise Linux Server Optional (v. 7) mod_ldap 2.4.6-45.el7_3.4, mod_session 2.4.6-45.el7_3.4, mod_proxy_html 2.4.6-45.el7_3.4 Red Hat Enterprise Linux Workstation (v. 7) httpd 2.4.6-45.el7_3.4, mod_ssl 2.4.6-45.el7_3.4, httpd-tools 2.4.6-45.el7_3.4, httpd-manual 2.4.6-45.el7_3.4 Red Hat Enterprise Linux Workstation Optional (v. 7) mod_ldap 2.4.6-45.el7_3.4, mod_session 2.4.6-45.el7_3.4, mod_proxy_html 2.4.6-45.el7_3.4
    fixed: vendor fix RHSA-2017:0906
  • Red Hat JBoss Core Services
    fixed: vendor fix RHSA-2018:2486
  • Red Hat JBoss Core Services on RHEL 6 Server jbcs-httpd24-apr 1.6.3-14.jbcs.el6, jbcs-httpd24-httpd 2.4.29-17.jbcs.el6, jbcs-httpd24-apr-util 1.6.1-9.jbcs.el6, jbcs-httpd24-nghttp2 1.29.0-8.jbcs.el6, jbcs-httpd24-mod_ssl 2.4.29-17.jbcs.el6, jbcs-httpd24-openssl 1.0.2n-11.jbcs.el6, +25 more
    fixed: vendor fix RHSA-2018:2186
show 2 more
  • Red Hat JBoss Core Services on RHEL 7 Server jbcs-httpd24-apr 1.6.3-14.jbcs.el7, jbcs-httpd24-httpd 2.4.29-17.jbcs.el7, jbcs-httpd24-apr-util 1.6.1-9.jbcs.el7, jbcs-httpd24-nghttp2 1.29.0-8.jbcs.el7, jbcs-httpd24-mod_ssl 2.4.29-17.jbcs.el7, jbcs-httpd24-openssl 1.0.2n-11.jbcs.el7, +25 more
    fixed: vendor fix RHSA-2018:2185
  • Red Hat Enterprise Linux 8 httpd, mod_md, mod_ssl, mod_ldap, mod_http2, httpd-tools, +4 more Red Hat Software Collections httpd24-httpd, httpd24-mod_md, httpd24-mod_ssl, httpd24-mod_ldap, httpd24-httpd-tools, httpd24-mod_session, +2 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

19.88% chance of exploitation in the next 30 days, higher than 97% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

CVSS scores

assigned by version score vector
NVD 3.0 6.1 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N

Affected products

  • Apache Software Foundation Apache HTTP Server

Classification

Weakness
  • CWE-93 Improper Neutralization of CRLF Sequences
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.