Apache | Httpd 2.4.18 Exploit

Other issues, often tracked through Vulmon, highlight that fuzzed network input can cause the server to access freed memory in string comparisons. While not always directly leading to remote code execution (RCE), this can lead to segmentation faults (crashes) or potential privilege escalation. 3. Anatomy of a Potential Exploit

FROM ubuntu:16.04 RUN apt-get update && apt-get install -y apache2=2.4.18-2ubuntu3 # Enable mod_cgi, mod_http2, and set AllowOverride All COPY vulnerable.cgi /usr/lib/cgi-bin/ CMD ["/usr/sbin/apache2ctl", "-D", "FOREGROUND"]

The primary exploit risks associated with the stem from critical structural vulnerabilities in its early HTTP/2 ( mod_http2 ) implementation and its scoreboard memory management . Released as part of the Apache 2.4 stable branch, version 2.4.18 contains multiple legacy security flaws that allow remote attackers to cause widespread denial-of-service (DoS) or enable local users to achieve full root privilege escalation. Key Apache HTTPD 2.4.18 Vulnerabilities CVE Identifier Vulnerability Type Impact Level Primary Component Affected CVE-2016-1546 Thread Starvation / DoS Medium / High mod_http2 Flow Control CVE-2019-0211 Local Privilege Escalation Critical Core Scoreboard / mod_prefork CVE-2016-0736 Padding Oracle Attack Medium mod_session_crypto CVE-2016-8743 Request Smuggling / Splitting Medium HTTP/1.1 Protocol Parser Deep-Dive Analysis of Primary Exploits 1. The HTTP/2 Thread Starvation Flaw (CVE-2016-1546)

The following matrix provides a clear breakdown of the primary exploit surfaces found in a default or common deployment of Apache 2.4.18: Vulnerability ID Vulnerability Type Impacted Module Attack Vector CVSS Severity Local Privilege Escalation Core / Scoreboard Local (Script execution) High (7.8) CVE-2016-4979 Security Bypass mod_http2 + mod_ssl Remote (Unauthenticated) Medium (5.9) CVE-2016-8740 Denial of Service (DoS) mod_http2 Remote (Unauthenticated) High (7.5) CVE-2019-10082 Use-After-Free Memory Leak mod_http2 Remote (Fuzzed Input) Critical (9.1) Penetration Testing and Vulnerability Identification apache httpd 2.4.18 exploit

The following sections explore each of the most severe vulnerabilities in greater detail.

In accordance with legacy RFC 3875 section 4.1.18, Apache sets environment variables based on the request headers sent by clients. A header named Proxy: evil.com causes Apache to assign HTTP_PROXY=evil.com to the execution environment of backend scripts.

This can lead to a server crash (Denial of Service) or, under specific memory layouts, the execution of malicious code. Other issues, often tracked through Vulmon, highlight that

During a graceful restart ( apache2ctl graceful ), the main root process alters its worker scoreboards. A malicious actor who already has low-privilege access to a worker process (for example, via a compromised PHP script) can manipulate the scoreboard memory.

Prevent attackers from easily identifying your software version via passive scanning. Modify your httpd.conf or security.conf file: ServerTokens Prod ServerSignature Off Use code with caution.

Understanding the Apache HTTPD 2.4.18 Exploit and Vulnerabilities Anatomy of a Potential Exploit FROM ubuntu:16

Once they had exploited the vulnerability, they had uploaded a malicious Lua script that allowed them to execute system commands on the server. The script was cleverly disguised as a legitimate configuration file, but John was able to spot it using his monitoring tools.

Because this version falls within the 2.4.17 to 2.4.38 range , it is susceptible to several high-impact exploits, most notably in local privilege escalation and memory handling. 1. Local Privilege Escalation (CVE-2019-0211)

Apache HTTP Server 2.4.18 was released on December 13, 2015. As a version over a decade old, it is considered and no longer receives security backports from the Apache Software Foundation. While no single “universal remote code execution (RCE)” exploit exists exclusively for 2.4.18, the version is vulnerable to a chain of publicly disclosed high-severity vulnerabilities (CVE-2016-5387, CVE-2016-8743, CVE-2017-9798, CVE-2017-15710). Adversaries actively target systems running this version due to its prevalence in legacy IoT devices, outdated LAMP stacks, and unmaintained web hosting environments.

When the server executes a graceful restart (commonly triggered daily by automatic utilities like logrotate ), the parent process uses the corrupted scoreboard data to manage worker threads. This triggers an out-of-bounds array access, allowing a local attacker to execute arbitrary code with the privileges of the parent process—which typically runs as .