The Apache HTTP Server 2.4.18 through 2.4.20, when mod_http2 and mod_ssl are enabled…
Priority MEDIUM 51CWE-284Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- None · High · None
- Fix status
- Fixed
Attack profile from CVSS 3.0 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-284.
Summary
The Apache HTTP Server 2.4.18 through 2.4.20, when mod_http2 and mod_ssl are enabled, does not properly recognize the "SSLVerifyClient require" directive for HTTP/2 request authorization, which allows remote attackers to bypass intended access restrictions by leveraging the ability to send multiple requests over a single connection and aborting a renegotiation.
Why it matters now
EPSS 0.18802 97th percentileScored 2026-11-07
Fix Fixed Red Hat: 1 advisory
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
Remediation
Red Hat 1 advisory
- RHSA-2016:1420 Released 2016-07-18 · Red Hat rating Importanthttpd24-httpd security update
- Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 6) httpd24-httpd-2.4.18-11.el6, httpd24-httpd-devel-2.4.18-11.el6, httpd24-httpd-manual-2.4.18-11.el6 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) httpd24-httpd-2.4.18-11.el7, httpd24-httpd-devel-2.4.18-11.el7, httpd24-httpd-manual-2.4.18-11.el7 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.6) httpd24-httpd-2.4.18-11.el6, httpd24-httpd-devel-2.4.18-11.el6, httpd24-httpd-manual-2.4.18-11.el6 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.7) httpd24-httpd-2.4.18-11.el6, httpd24-httpd-devel-2.4.18-11.el6, httpd24-httpd-manual-2.4.18-11.el6 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.1) httpd24-httpd-2.4.18-11.el7, httpd24-httpd-devel-2.4.18-11.el7, httpd24-httpd-manual-2.4.18-11.el7 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.2) httpd24-httpd-2.4.18-11.el7, httpd24-httpd-devel-2.4.18-11.el7, httpd24-httpd-manual-2.4.18-11.el7 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 6) httpd24-httpd-2.4.18-11.el6, httpd24-httpd-devel-2.4.18-11.el6, httpd24-httpd-manual-2.4.18-11.el6 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) httpd24-httpd-2.4.18-11.el7, httpd24-httpd-devel-2.4.18-11.el7, httpd24-httpd-manual-2.4.18-11.el7 +5
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 6) | Fixed | RHSA-2016:1420 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) | Fixed | RHSA-2016:1420 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.6) | Fixed | RHSA-2016:1420 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.7) | Fixed | RHSA-2016:1420 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.1) | Fixed | RHSA-2016:1420 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.2) | Fixed | RHSA-2016:1420 |
| Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 6) | Fixed | RHSA-2016:1420 |
| Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) | Fixed | RHSA-2016:1420 |
Not affected: 10 products
- Red Hat Directory Server 8
- Red Hat Enterprise Linux 5
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat JBoss Core Services
- Red Hat JBoss Enterprise Application Platform 5
- Red Hat JBoss Enterprise Application Platform 6
- Red Hat JBoss Enterprise Web Server 1
- Red Hat JBoss Enterprise Web Server 2
- Red Hat JBoss Enterprise Web Server 3
Timeline
- 2026-10-02 Threatist record created from CVE-2016-4979
- 2026-10-03 Alias added: GHSA-r48c-7gpg-9q4x
References
Advisory 2
Other 20
- 20160706 CVE-2016-4979: HTTPD webserver - X509 Client certificate based authentication can be bypassed when HTTP/2 is used [vs]
- http://www.oracle.com/technetwork/security-advisory/cpuoct2016-2881722.html
- http://www.apache.org/dist/httpd/CHANGES_2.4
- http://www.oracle.com/technetwork/topics/security/bulletinoct2016-3090566.html
- [oss-security] 20160705 CVE-2016-4979: HTTPD webserver - X509 Client certificate based authentication can be bypassed when HTTP/2 is used [vs]
- https://github.com/apache/httpd/commit/2d0e4eff04ea963128a41faaef21f987272e05a2
- http://packetstormsecurity.com/files/137771/Apache-2.4.20-X509-Authentication-Bypass.html
- https://security.netapp.com/advisory/ntap-20180601-0001/
- [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/vulnerabilities_24.html
- [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/vulnerabilities_24.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/vulnerabilities_24.html
- [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/vulnerabilities_24.html
- [httpd-cvs] 20210330 svn commit: r1073139 [1/13] - in /websites/staging/httpd/trunk/content: ./ security/json/
- [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.html
- [httpd-cvs] 20210330 svn commit: r1888194 [10/13] - /httpd/site/trunk/content/security/json/
- [httpd-cvs] 20210330 svn commit: r1073139 [10/13] - in /websites/staging/httpd/trunk/content: ./ security/json/
- [httpd-cvs] 20210330 svn commit: r1073149 [1/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/
- [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
- [httpd-cvs] 20210330 svn commit: r1073149 [10/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/
- [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/vulnerabilities_24.html
More Apache Http Server vulnerabilities
- TI-2021-18535 Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) KEVCVSS 3.1CRITICAL 9.8
- TI-2021-18417 Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 KEVCVSS 3.1CRITICAL 9.8
- TI-2024-25716 Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path. KEVCVSS 3.1CRITICAL 9.1
- TI-2021-17490 mod_proxy SSRF KEVCVSS 3.1CRITICAL 9.0
- TI-2019-00184 Use after free in Apache HTTP Server KEVCVSS 3.1HIGH 7.8
- TI-2009-03392 The TLS protocol, and the SSL protocol 3.0 and possibly earlier, as used in Microsoft… CVSS 3.1CRITICAL 9.8
Sources
- CVE-2016-4979 · CVE Program
- CVE-2016-4979 · NVD
- FIRST EPSS
- GHSA-r48c-7gpg-9q4x · GitHub Advisory Database · CC BY 4.0
- CVE-2016-4979 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences