Attackers leverage this backdoor by injecting commands directly into the User-Agentt header of a standard HTTP request. PHP 8.1.0-dev Backdoor Remote Code Execution - GitHub
The exploit targets a malicious modification in the zval_get_string function within the PHP source. This backdoor looks for a specific HTTP header named User-Agentt (note the double "t"). If this header is present and starts with the keyword zerodium , the code executes the rest of the string as a PHP command on the server. Technical Breakdown of the Exploit php 8.1.0-dev exploit
The is a critical supply-chain vulnerability stemming from a backdoor intentionally planted in the PHP source code in March 2021. This flaw allows an unauthenticated attacker to achieve Remote Code Execution (RCE) by sending a specially crafted HTTP header. While quickly patched, the version remains a common target in security labs and CTF challenges due to its straightforward exploitation. Vulnerability Mechanism If this header is present and starts with