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    CVE-2016-4979

    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.

    Published:Jul 5, 2016
    Last Modified:Apr 12, 2025
    EPS:Jul 6, 2016
    EPSS Score:0.16906
    CVSS Score:7.5

    Affected Products

    Vendor
    Apache
    Product
    Http Server
    Vendor
    Redhat
    Product
    Rhel Software Collections

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-114 Authentication Abuse
    CAPEC-115 Authentication Bypass
    CAPEC-151 Identity Spoofing
    CAPEC-19 Embedding Scripts within Scripts
    CAPEC-194 Fake the Source of Data
    CAPEC-22 Exploiting Trust in Client
    CAPEC-441 Malicious Logic Insertion
    CAPEC-478 Modification of Windows Service Configuration
    CAPEC-479 Malicious Root Certificate
    CAPEC-502 Intent Spoof
    CAPEC-503 WebView Exposure
    CAPEC-536 Data Injected During Configuration
    CAPEC-546 Incomplete Data Deletion in a Multi-Tenant Environment
    CAPEC-550 Install New Service
    CAPEC-551 Modify Existing Service
    CAPEC-552 Install Rootkit
    CAPEC-556 Replace File Extension Handlers
    CAPEC-558 Replace Trusted Executable
    CAPEC-562 Modify Shared File
    CAPEC-563 Add Malicious File to Shared Webroot
    CAPEC-564 Run Software at Logon
    CAPEC-57 Utilizing REST's Trust in the System Resource to Obtain Sensitive Data
    CAPEC-578 Disable Security Software
    CAPEC-593 Session Hijacking
    CAPEC-633 Token Impersonation
    CAPEC-650 Upload a Web Shell to a Web Server
    CAPEC-94 Adversary in the Middle (AiTM)

    Related CVEs

    CVE-2026-48913 (CVSS 7.3) — Use After Free vulnerability in Apache HTTP Server module mod_http2 when file handles are already exhausted. …
    CVE-2026-42536 (CVSS 7.5) — Heap-based Buffer Overflow vulnerability in Apache HTTP Server with mod_xml2enc, xml2StartParse, and untrusted…
    CVE-2026-44185 (CVSS 7.3) — Buffer Over-read vulnerability in Apache HTTP Server via outbound OCSP requests to an attacker controlled OCSP…
    CVE-2026-34355 (CVSS 7.5) — A buffer overflow in mod_proxy_html in Apache HTTP Server 2.4.67 and earlier allows an attack by an untrusted …
    CVE-2026-44631 (CVSS 9.8) — Buffer Underwrite vulnerability in Apache HTTP Server on crafted regular expressions in the configuration. Th…
    CVE-2026-44119 (CVSS 5.5) — Improper Privilege Management vulnerability in Apache HTTP Server 2.4.67 and earlier allows local .htaccess au…
    CVE-2026-43951 (CVSS 6.5) — Out-of-bounds Read vulnerability in Apache HTTP Server with mod_headers and mod_mime and multiple response lan…
    CVE-2026-42535 (CVSS 9.1) — A path handling issue in mod_dav_fs in Apache 2.4.67 and earlier allows a WebDAV content author to directly ma…
    CVE-2026-34356 (CVSS 7.5) — Heap-based Buffer Overflow vulnerability in Apache HTTP Server with malicious backend servers and ProxyPassRev…
    CVE-2026-44186 (CVSS 7.3) — Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in the mod_proxy_ftp module in Apache HTT…

    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
    https://lists.apache.org/thread.html/84a3714f0878781f6ed84473d1a503d2cc382277e100450209231830%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/r04e89e873d54116a0635ef2f7061c15acc5ed27ef7500997beb65d6f%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/r76142b8c5119df2178be7c2dba88fde552eedeec37ea993dfce68d1d%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/r9f93cf6dde308d42a9c807784e8102600d0397f5f834890708bf6920%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rb14daf9cc4e28d18cdc15d6a6ca74e565672fabf7ad89541071d008b%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rc998b18880df98bafaade071346690c2bc1444adaa1a1ea464b93f0a%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rcc44594d4d6579b90deccd4536b5d31f099ef563df39b094be286b9e%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rd18c3c43602e66f9cdcf09f1de233804975b9572b0456cc582390b6f%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/re1e3a24664d35bcd0a0e793e0b5fc6ca6c107f99a1b2c545c5d4b467%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/re3d27b6250aa8548b8845d314bb8a350b3df326cacbbfdfe4d455234%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rf6449464fd8b7437704c55f88361b66f12d5b5f90bcce66af4be4ba9%40%3Ccvs.httpd.apache.org%3E
    https://security.gentoo.org/glsa/201610-02
    https://security.netapp.com/advisory/ntap-20180601-0001/
    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
    https://lists.apache.org/thread.html/84a3714f0878781f6ed84473d1a503d2cc382277e100450209231830%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/r04e89e873d54116a0635ef2f7061c15acc5ed27ef7500997beb65d6f%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/r76142b8c5119df2178be7c2dba88fde552eedeec37ea993dfce68d1d%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/r9f93cf6dde308d42a9c807784e8102600d0397f5f834890708bf6920%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rb14daf9cc4e28d18cdc15d6a6ca74e565672fabf7ad89541071d008b%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rc998b18880df98bafaade071346690c2bc1444adaa1a1ea464b93f0a%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rcc44594d4d6579b90deccd4536b5d31f099ef563df39b094be286b9e%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rd18c3c43602e66f9cdcf09f1de233804975b9572b0456cc582390b6f%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/re1e3a24664d35bcd0a0e793e0b5fc6ca6c107f99a1b2c545c5d4b467%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/re3d27b6250aa8548b8845d314bb8a350b3df326cacbbfdfe4d455234%40%3Ccvs.httpd.apache.org%3E
    https://lists.apache.org/thread.html/rf6449464fd8b7437704c55f88361b66f12d5b5f90bcce66af4be4ba9%40%3Ccvs.httpd.apache.org%3E
    https://security.gentoo.org/glsa/201610-02
    https://security.netapp.com/advisory/ntap-20180601-0001/

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High