CVE-2006-6966 in phpGraphy
Summary
by MITRE
phpGraphy before 0.9.13a does not properly unset variables when the input data includes a numeric parameter with a value matching an alphanumeric parameter s hash value, which allows remote attackers to execute arbitrary PHP code by uploading a config.php file via the pictures[] parameter to index.php. NOTE: it could be argued that this vulnerability is due to a bug in the unset PHP command (CVE-2006-3017) and the proper fix should be in PHP; if so, then this should not be treated as a vulnerability in phpGraphy.
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Analysis
by VulDB Data Team • 08/18/2018
The vulnerability described in CVE-2006-6966 represents a critical security flaw in phpGraphy versions prior to 0.9.13a that stems from improper variable handling during input processing. This issue manifests when the application encounters numeric parameters whose values match the hash values of alphanumeric parameters, creating a condition where variables fail to be properly unset. The vulnerability is particularly dangerous because it enables remote code execution through a carefully crafted file upload attack vector. Attackers can exploit this weakness by manipulating the pictures[] parameter in requests to index.php, allowing them to upload a malicious config.php file that gets executed in the context of the web server.
The technical root cause of this vulnerability lies in PHP's variable handling mechanism and how it interacts with the unset function when dealing with hash collisions between different data types. When phpGraphy processes input parameters, it fails to properly manage variable scope and cleanup operations, particularly when numeric and alphanumeric parameters share identical hash values. This creates a scenario where variables intended to be destroyed remain accessible in memory, potentially exposing sensitive application logic or allowing attackers to manipulate the execution flow. The vulnerability specifically relates to the internal hash table implementation in PHP where different types of data can produce identical hash values, leading to unexpected behavior in variable cleanup operations.
The operational impact of this vulnerability is severe as it provides attackers with a direct path to arbitrary code execution on the target server. By uploading a config.php file through the pictures[] parameter, an attacker can effectively gain control over the web application's execution environment and potentially compromise the entire server. This type of vulnerability allows for privilege escalation, data theft, and persistent access to the compromised system. The attack requires minimal privileges and can be executed remotely, making it particularly dangerous for web applications that process user input without proper sanitization. The vulnerability essentially transforms a legitimate file upload functionality into a weapon for remote exploitation.
Security practitioners should implement multiple layers of defense to mitigate this vulnerability. The primary recommendation is to upgrade to phpGraphy version 0.9.13a or later where the issue has been properly addressed. Additionally, input validation should be strengthened to prevent unexpected parameter types from being processed, and proper parameter sanitization should be implemented before any variable assignment occurs. Organizations should also consider implementing web application firewalls to detect and block suspicious parameter combinations that might trigger this vulnerability. The fix for this issue aligns with CWE-121 and CWE-122 categories related to buffer overflow conditions and improper restriction of operations within a limited error handling scope, and it maps to attack techniques in the ATT&CK framework under initial access and execution phases. Given the nature of this vulnerability, it is crucial to review all applications using similar parameter handling patterns and ensure that proper variable cleanup mechanisms are in place to prevent similar hash collision issues from occurring in other software components.