CVE-2016-4975: mod_userdir CRLF injection
Vulnerability summary
CVE-2016-4975 is a medium (CVSS 6.1) vulnerability in apache software foundation apache http server. EPSS estimates a 19.80% chance of exploitation in the next 30 days, higher than 97.4% of scored vulnerabilities.
Not severe (CVSS 6.1, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 6 · Related 4Timeline
- 14-08-2018PublishedVulnerability first disclosed.
- 16-09-2024Last modifiedVulnerability information updated.
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).
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated6.1MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- OSV · DebianEcosystem advisory · calculated6.1MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS trend
Probability
19.80%
Chance of exploitation in the next 30 days
Percentile
97%
Versus all other CVEs
30-day change
No change 0.00 pp
From 19.80% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.
Apache1 product
- http_serverEOL2.2.0 | 2.2.2 | 2.2.3 | 2.2.4 | 2.2.6 | 2.2.8 | 2.2.9 | 2.2.10 | 2.2.11 | 2.2.12 | 2.2.13 | 2.2.14 | 2.2.15 | 2.2.16 | 2.2.17 | 2.2.18 | 2.2.19 | 2.2.20 | 2.2.21 | 2.2.22 | 2.2.23 | 2.2.24 | 2.2.25 | 2.2.26 | 2.2.27 | 2.2.29 | 2.2.31 | 2.4.1 | 2.4.2 | 2.4.3 | 2.4.4 | 2.4.6 | 2.4.7 | 2.4.9 | 2.4.10 | 2.4.12 | 2.4.16 | 2.4.17 | 2.4.18 | 2.4.20 | 2.4.23
Apache software foundation1 product
- apache http serverFixed 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)
Debian1 product
- apache2< 2.4.25-1
Ubuntu1 product
- apache2< 2.4.7-1ubuntu4.15 | < 2.4.18-2ubuntu3.2
4 vendors · 4 products
