CVE-2007-0639 in GuppY
Summary
by MITRE
Multiple static code injection vulnerabilities in error.php in GuppY 4.5.16 and earlier allow remote attackers to inject arbitrary PHP code into a .inc file in the data/ directory via (1) a REMOTE_ADDR cookie or (2) a cookie specifying an element of the msg array with an error number in the first dimension and 0 in the second dimension, as demonstrated by msg[999][0].
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Analysis
by VulDB Data Team • 08/20/2024
The vulnerability identified as CVE-2007-0639 represents a critical static code injection flaw within the GuppY content management system version 4.5.16 and earlier. This vulnerability resides in the error.php script which processes error handling within the application. The flaw stems from inadequate input validation and sanitization mechanisms that fail to properly escape or filter user-supplied data before incorporating it into dynamically generated PHP code. The vulnerability specifically affects how the application handles error messages and cookie data, creating opportunities for remote attackers to inject malicious PHP code that gets executed within the application context.
The technical implementation of this vulnerability exploits two distinct attack vectors that both leverage cookie manipulation to achieve code injection. The first vector involves manipulation of the REMOTE_ADDR cookie, which is typically used to identify client IP addresses but becomes exploitable when the application directly incorporates its value into code generation without proper sanitization. The second vector targets a specific cookie structure that references elements within the msg array using the pattern msg[999][0], where the first dimension represents an error number and the second dimension is hardcoded to zero. This array structure is processed by the error.php script in a manner that directly incorporates user-controllable values into PHP code execution contexts, bypassing normal security boundaries.
The operational impact of this vulnerability extends far beyond simple code injection, as it provides attackers with complete control over the affected web server's functionality. Successful exploitation allows remote attackers to execute arbitrary PHP code with the privileges of the web server process, potentially leading to complete system compromise. Attackers can leverage this vulnerability to establish persistent backdoors, exfiltrate sensitive data, modify content, or use the compromised server as a staging point for further attacks within the network. The vulnerability's remote nature means that attackers can exploit it without requiring local access or authentication, making it particularly dangerous in production environments where the web application is publicly accessible.
The vulnerability aligns with CWE-94, which describes the weakness of "Improper Control of Generation of Code ('Code Injection')" and is closely related to the ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Unix Shell" and T1505.003 for "Server Software Component: Web Shell." The attack surface is significantly broadened by the fact that the injection occurs during error handling, which is a common and frequently executed code path within web applications. This makes the vulnerability particularly effective as attackers can trigger the injection through normal application error conditions, making detection more difficult. The exploitation requires minimal privileges and can be automated, making it attractive to both automated attack tools and sophisticated threat actors.
Mitigation strategies for this vulnerability require immediate patching of the GuppY application to version 4.5.17 or later, where the code injection flaws have been addressed through proper input validation and sanitization. Organizations should implement comprehensive cookie validation mechanisms that reject or sanitize any cookie values that could be used for code injection attacks. Network-level protections including web application firewalls and intrusion detection systems can help detect and block exploitation attempts, though these should not be relied upon as the sole defense mechanism. Additionally, implementing proper input validation at all points where user data is processed, particularly in error handling code, is essential. The vulnerability demonstrates the critical importance of validating and sanitizing all user-supplied input before incorporating it into any dynamic code generation processes, regardless of the expected data type or source.