Eventually, the entry point was , but an outdated OpenSSL 1.0.2g (DROWN attack) and a misconfigured mod_dav allowed file upload. The exploit chain used Apache as a vector, but no native 2.4.18 RCE.
In a standard .htaccess or configuration file, an administrator might restrict file uploads using a pattern like \<FilesMatch ".+\.php$"\> . The intention is to block any file ending with ".php". However, due to a flaw in the pattern matching logic, the $ anchor can match a newline character ( \x0A ) in a malicious filename rather than only matching the end of the filename. Consequently, a file named malicious.php%0a bypasses the restriction and is interpreted as a PHP script by the server. apache httpd 2.4.18 exploit
If a PHP or CGI application uses the HTTP_PROXY environment variable to configure outgoing HTTP requests (for example, when using libraries like Guzzle or cURL), an attacker can set a malicious Proxy: http://evil.com/ header. The application will then route all outgoing requests through the attacker-controlled proxy, potentially leaking sensitive information or enabling man-in-the-middle attacks. Eventually, the entry point was , but an outdated OpenSSL 1
Thus, a successful exploit against a generic 2.4.18 often fails against a patched distribution version, even if the version string is identical. The intention is to block any file ending with "
: An attacker with low-level permissions on the server (such as through a compromised PHP script) can write to the shared memory used by Apache's parent process. When the server performs its daily log rotation and restarts, the parent process—which runs with root privileges —executes the attacker's code.
While not a direct RCE, memory leaks can bypass ASLR (Address Space Layout Randomization), making it easier to chain with other exploits. In 2017, researchers demonstrated that by triggering OptionsBleed repeatedly, one could reconstruct HTTP/2 connection memory.