CVE-2008-6659 in Simple Machines
Summary
by MITRE
Directory traversal vulnerability in index.php in Simple Machines Forum (SMF) 1.0 before 1.0.15 and 1.1 before 1.1.7 allows remote authenticated users to configure arbitrary local files for execution via directory traversal sequences in the value of the theme_dir field during a jsoption action, related to Sources/QueryString.php and Sources/Themes.php, as demonstrated by a local .gif file in attachments/ with PHP code that was uploaded through a profile2 action to index.php.
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Analysis
by VulDB Data Team • 11/10/2024
The CVE-2008-6659 vulnerability represents a critical directory traversal flaw within Simple Machines Forum versions prior to 1.0.15 and 1.1.7, specifically affecting the theme configuration functionality. This vulnerability exists in the core forum software's handling of user-supplied input during the jsoption action, where the theme_dir field parameter is processed without adequate sanitization or validation. The flaw allows authenticated attackers to manipulate file paths and execute arbitrary code by exploiting improper input handling in the Sources/QueryString.php and Sources/Themes.php files. The vulnerability is particularly dangerous because it operates within the context of authenticated users, meaning that an attacker must first gain access to a valid user account but does not require administrative privileges to exploit this weakness.
The technical exploitation of this vulnerability occurs through carefully crafted directory traversal sequences that manipulate the theme_dir parameter during the jsoption action. When a user submits a malicious value for theme_dir, the application fails to properly validate or sanitize the input before using it in file system operations. This allows attackers to traverse directories and access files that should normally be protected or restricted. The vulnerability is demonstrated through the use of local .gif files in the attachments/ directory that contain embedded PHP code, which can be executed when the forum processes the malicious theme configuration. This type of attack leverages the principle of inadequate input validation, which is classified as CWE-22 under the Common Weakness Enumeration framework.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with the ability to modify or access arbitrary local files on the server hosting the forum. An attacker could potentially upload malicious files through the profile2 action and then leverage the directory traversal to execute these files, effectively gaining persistent access to the system. This vulnerability creates a pathway for attackers to escalate privileges, install backdoors, or extract sensitive data from the server. The attack surface is particularly concerning because it affects the core theme management functionality, which is frequently used by forum administrators and users alike, making the exploitation both accessible and potentially devastating to the security posture of the affected installation.
The exploitation of this vulnerability aligns with several techniques documented in the MITRE ATT&CK framework, particularly those related to privilege escalation and persistence. The attack pattern involves manipulating application configuration to achieve unauthorized file access and execution, which maps to techniques for gaining access to system resources and maintaining access over time. Organizations running vulnerable SMF installations face significant risk of compromise, as this vulnerability allows for arbitrary code execution without requiring extensive reconnaissance or specialized tools. The vulnerability also highlights the importance of proper input validation and secure coding practices, as the flaw stems from insufficient sanitization of user-supplied parameters before they are used in file system operations. Security practitioners should prioritize patching affected installations and implementing additional monitoring for suspicious file access patterns in the attachments directory, as this vulnerability can be used to establish persistent access to compromised systems through the execution of malicious PHP code embedded within seemingly benign image files.