CVE-2001-1246 in PHP
Summary
by MITRE
PHP 4.0.5 through 4.1.0 in safe mode does not properly cleanse the 5th parameter to the mail() function, which allows local users and possibly remote attackers to execute arbitrary commands via shell metacharacters.
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Analysis
by VulDB Data Team • 09/27/2025
The vulnerability described in CVE-2001-1246 represents a critical command injection flaw in PHP versions ranging from 4.0.5 through 4.1.0 when operating in safe mode. This issue specifically targets the mail() function's fifth parameter handling, which is used for additional headers in email transmission. The flaw occurs because PHP fails to properly sanitize or escape shell metacharacters that may be present in this parameter, creating an avenue for malicious code execution.
The technical implementation of this vulnerability stems from inadequate input validation and sanitization within PHP's mail() function implementation. When PHP processes the fifth parameter of the mail() function, it passes this parameter directly to the system's mail command without proper filtering or escaping of special shell characters. This oversight allows attackers to inject shell commands that get executed with the privileges of the web server process. The vulnerability is particularly concerning because it can be exploited even when PHP is running in safe mode, which is designed to restrict certain system functions and limit potential attack vectors.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with the ability to perform arbitrary code execution on the affected system. Local users who can execute PHP scripts on the server can leverage this vulnerability to gain elevated privileges and potentially compromise the entire web server environment. Remote attackers may also exploit this vulnerability if they can influence the content of the fifth parameter through user input or other attack vectors, making it a significant threat to web application security. The vulnerability essentially undermines the security model of safe mode by allowing privilege escalation through a single function call.
This vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and maps to ATT&CK technique T1059.007 for command and script injection. The flaw demonstrates the critical importance of proper input sanitization and the dangers of relying on security mechanisms like safe mode that may have inherent weaknesses. Organizations should immediately upgrade to PHP versions beyond 4.1.0 where this vulnerability has been resolved, implement proper input validation for all user-supplied data, and consider additional security measures such as web application firewalls and runtime monitoring to detect potential exploitation attempts.
The remediation strategy involves immediate patching of affected PHP installations to versions that properly sanitize the mail() function's fifth parameter. Additionally, administrators should review all PHP applications to ensure no code relies on unsafe parameter handling and implement comprehensive input validation measures. Security monitoring should be enhanced to detect unusual command execution patterns that might indicate exploitation attempts. The vulnerability serves as a historical example of how even seemingly minor implementation flaws in system functions can create significant security risks when combined with inadequate input sanitization practices.