CVE-2002-0985 in PHP
Summary
by MITRE
Argument injection vulnerability in the mail function for PHP 4.x to 4.2.2 may allow attackers to bypass safe mode restrictions and modify command line arguments to the MTA (e.g. sendmail) in the 5th argument to mail(), altering MTA behavior and possibly executing commands.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/06/2018
The vulnerability described in CVE-2002-0985 represents a critical argument injection flaw in PHP's mail function affecting versions 4.x through 4.2.2. This issue stems from improper handling of command line arguments when invoking the mail transport agent, creating a pathway for malicious actors to manipulate the underlying system commands. The vulnerability specifically targets the fifth argument of the mail() function which is intended to pass additional parameters to the mail transfer agent, particularly sendmail in Unix-like environments. When attackers can control this argument, they gain the ability to inject arbitrary command line parameters that can alter the behavior of the mail transfer agent.
The technical exploitation of this vulnerability occurs through the manipulation of the fifth parameter in PHP's mail() function, which is passed directly to the system command without proper sanitization or validation. This allows attackers to inject command line switches and arguments that can modify how the mail transfer agent processes messages. The vulnerability directly relates to CWE-74, which describes improper neutralization of special elements used in OS commands, and CWE-94, which covers improper control of generation of code. The flaw essentially enables attackers to bypass PHP's safe mode restrictions by leveraging the underlying operating system's command execution capabilities. When the mail function executes system commands to deliver messages, the unvalidated fifth argument can contain malicious payloads that get interpreted by the mail transfer agent, potentially leading to arbitrary command execution.
The operational impact of this vulnerability is severe as it allows attackers to circumvent PHP's security mechanisms designed to restrict system access. Safe mode, which was intended to limit the ability of PHP scripts to access system resources, becomes ineffective when this argument injection occurs. Attackers can use this vulnerability to execute arbitrary commands on the server with the privileges of the web server process, potentially leading to full system compromise. The vulnerability affects systems where PHP is configured to use sendmail or similar mail transfer agents, making it particularly dangerous in shared hosting environments or systems where multiple users run PHP applications. This type of vulnerability aligns with ATT&CK technique T1059.007, which covers command and scripting interpreter for execution, and T1566.001, which covers spearphishing attachments, as attackers can leverage this to execute malicious commands after gaining initial access through other vectors.
The primary mitigation strategies involve upgrading to PHP versions 4.2.3 or later where this vulnerability has been patched, implementing proper input validation and sanitization for all user-supplied data that might be passed to mail functions, and configuring the mail transfer agent with appropriate security restrictions. Administrators should also consider using alternative mail delivery methods such as SMTP libraries that don't rely on direct system command execution, and implementing proper network segmentation to limit the potential impact of successful exploitation. Additionally, disabling the mail function entirely when it's not required, or using PHP's mail() function with strict parameter validation, can help prevent exploitation of this vulnerability. The patch for this vulnerability specifically addresses the improper handling of the fifth argument in the mail() function by implementing proper escaping and validation of command line parameters before they are passed to the mail transfer agent.