CVE-2007-3543 in WordPress
Summary
by MITRE
Unrestricted file upload vulnerability in WordPress before 2.2.1 and WordPress MU before 1.2.3 allows remote authenticated users to upload and execute arbitrary PHP code by making a post that specifies a .php filename in the _wp_attached_file metadata field; and then sending this file s content, along with its post_ID value, to (1) wp-app.php or (2) app.php.
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Analysis
by VulDB Data Team • 03/15/2021
The vulnerability identified as CVE-2007-3543 represents a critical unrestricted file upload flaw affecting WordPress versions prior to 2.2.1 and WordPress MU versions prior to 1.2.3. This vulnerability operates through a sophisticated attack vector that leverages the metadata handling mechanisms within WordPress's media attachment system. The flaw specifically targets the _wp_attached_file metadata field which is designed to store file paths for media attachments but becomes exploitable when manipulated by authenticated users. The vulnerability is particularly dangerous because it allows authenticated attackers to bypass normal file upload restrictions and execute arbitrary PHP code on the target server, effectively granting them remote code execution capabilities.
The technical implementation of this vulnerability exploits the lack of proper validation and sanitization of file names within the WordPress media handling pipeline. When an authenticated user creates a post and manipulates the _wp_attached_file metadata field to include a .php filename, the system accepts this input without adequate verification. The attack requires the malicious user to first create a post with the manipulated metadata, then send the actual PHP payload content along with the corresponding post_ID value to either wp-app.php or app.php endpoints. These endpoints serve as XML-RPC interfaces that were designed to support remote posting capabilities but became entry points for arbitrary code execution due to insufficient input validation. The vulnerability stems from CWE-434 which specifically addresses insecure file upload handling, where the system fails to validate file types or content before storing uploaded files.
The operational impact of this vulnerability is severe and multifaceted, representing a complete compromise of the affected WordPress installation. Once exploited, attackers can execute arbitrary PHP code with the privileges of the web server process, potentially leading to full system compromise. The vulnerability enables attackers to upload backdoors, web shells, or other malicious payloads that can persist on the server and provide ongoing access. Additionally, the attack can be used to escalate privileges, steal sensitive data, modify content, or even establish a command and control channel. The fact that this vulnerability requires only authenticated access makes it particularly concerning as it can be exploited by compromised user accounts or insiders with legitimate access to the WordPress system. This vulnerability aligns with ATT&CK technique T1505.003 for server-side include attacks and T1059.007 for scripting with PHP, demonstrating how the exploitation chain can be used to establish persistent access and maintain control over the compromised system.
The mitigation strategies for CVE-2007-3543 primarily focus on immediate system updates and configuration hardening. Organizations must upgrade to WordPress 2.2.1 or later versions and WordPress MU 1.2.3 or later to receive the patched security measures. The fix implemented by WordPress developers addressed the insecure handling of the _wp_attached_file metadata field by introducing proper validation and sanitization of file names during the media attachment process. Additional mitigations include implementing restrictive file type validation at the web server level, configuring proper file permissions for upload directories, and deploying web application firewalls that can detect and block suspicious file upload patterns. Security practitioners should also consider implementing monitoring for unusual file upload activities and ensure that WordPress installations are regularly updated with the latest security patches. The vulnerability highlights the importance of input validation and the principle of least privilege in web application security, as proper validation of metadata fields could have prevented this attack vector from being exploited.