CVE-2000-0967 in PHP
Summary
by MITRE
PHP 3 and 4 do not properly cleanse user-injected format strings, which allows remote attackers to execute arbitrary commands by triggering error messages that are improperly written to the error logs.
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Analysis
by VulDB Data Team • 10/12/2025
The vulnerability described in CVE-2000-0967 represents a critical security flaw in PHP versions 3 and 4 that stems from improper handling of user-supplied input within error message contexts. This issue falls under the category of format string vulnerabilities, which occur when applications use user-provided data directly in formatting functions without proper sanitization. The flaw specifically manifests when PHP processes error messages that contain improperly escaped format specifiers, creating a pathway for malicious input to be interpreted as executable code during error log writing operations. This vulnerability is particularly dangerous because it leverages the fundamental error handling mechanisms of the PHP runtime environment to achieve remote code execution.
The technical implementation of this vulnerability exploits the way PHP processes error messages through functions like error_log() or when PHP itself generates error messages during script execution. When user input containing format specifiers such as %s, %d, or %x is incorporated into error messages without proper sanitization, attackers can inject malicious format specifiers that reference memory locations or trigger specific system behaviors. The vulnerability is classified as CWE-134, which specifically addresses the use of format strings with user-supplied data, and aligns with ATT&CK technique T1059.007 for command and script injection. Attackers can craft input that, when processed through PHP's error handling system, causes the format string to be interpreted as executable code, potentially leading to arbitrary command execution on the server.
The operational impact of CVE-2000-0967 is severe and far-reaching, as it allows remote attackers to execute arbitrary commands on vulnerable systems with the privileges of the web server process. This can result in complete system compromise, data exfiltration, and the ability to establish persistent backdoors. The vulnerability is particularly concerning because it can be exploited through various attack vectors including web forms, URL parameters, or any input field that PHP processes and subsequently logs in error messages. The attack requires no special privileges beyond the ability to send HTTP requests to the vulnerable web application, making it highly exploitable in real-world scenarios. The vulnerability also affects the integrity of system logs, as malicious input can be injected into the error log files, potentially obscuring legitimate security events and complicating forensic analysis.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security architecture improvements. The most effective immediate solution involves upgrading to PHP versions 5.0 or later, where format string handling has been significantly improved and the vulnerability has been eliminated. Organizations should also implement input validation and sanitization mechanisms that prevent user-supplied data from containing format specifiers, particularly in contexts where error messages are generated. The implementation of proper error handling practices, including the use of printf-style functions with explicit string arguments rather than user input, helps prevent the vulnerability. Additionally, organizations should consider implementing web application firewalls and intrusion detection systems that can monitor for suspicious input patterns that might indicate exploitation attempts. Regular security audits and vulnerability assessments should be conducted to identify and remediate similar issues in legacy systems, while also ensuring that proper logging and monitoring mechanisms are in place to detect any exploitation attempts.