CVE-2016-4979

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 18.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2016-07-06 · updated 2026-06-17
Weakness: CWE-284

Description

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.

Affected products

Apache HTTP Server: 2.4.18, 2.4.19, 2.4.20

References

http://httpd.apache.org/security/vulnerabilities_24.html
http://packetstormsecurity.com/files/137771/Apache-2.4.20-X509-Authentication-Bypass.html
http://seclists.org/fulldisclosure/2016/Jul/11
http://www.apache.org/dist/httpd/CHANGES_2.4
http://www.openwall.com/lists/oss-security/2016/07/05/5
http://www.oracle.com/technetwork/security-advisory/cpuoct2016-2881722.html
http://www.oracle.com/technetwork/topics/security/bulletinoct2016-3090566.html
http://www.securityfocus.com/bid/91566
http://www.securitytracker.com/id/1036225
https://access.redhat.com/errata/RHSA-2016:1420
https://github.com/apache/httpd/commit/2d0e4eff04ea963128a41faaef21f987272e05a2
https://lists.apache.org/thread.html/56c2e7cc9deb1c12a843d0dc251ea7fd3e7e80293cde02fcd65286ba%40%3Ccvs.httpd.apache.org%3E

Get alerted when CVE-2016-4979 or the next vulnerability affects your stack