CVE-2017-11658 in WP Rocket Plugin
Summary
by MITRE
In the WP Rocket plugin 2.9.3 for WordPress, the Local File Inclusion mitigation technique is to trim traversal characters (..) -- however, this is insufficient to stop remote attacks and can be bypassed by using 0x00 bytes, as demonstrated by a .%00.../.%00.../ attack.
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Analysis
by VulDB Data Team • 11/01/2019
The vulnerability identified as CVE-2017-11658 affects the WP Rocket plugin version 2.9.3 for WordPress, representing a critical security flaw in the plugin's handling of file paths and traversal attempts. This issue stems from an inadequate implementation of local file inclusion mitigation techniques that were designed to prevent attackers from accessing arbitrary files on the server through directory traversal sequences. The plugin's developers implemented a basic defense mechanism that simply trims traversal characters represented by double dots, which is a common approach to prevent path traversal attacks in web applications. However, this simplistic mitigation strategy fails to account for more sophisticated attack vectors that can bypass such basic protections through the exploitation of encoding mechanisms and null byte injection techniques. The vulnerability specifically targets the plugin's handling of file paths during image processing and caching operations, where it processes user-supplied input to determine which files to access or manipulate.
The technical exploitation of this vulnerability relies on the manipulation of input parameters through null byte sequences encoded in hexadecimal format, specifically using 0x00 bytes to bypass the basic traversal character trimming mechanism. Attackers can construct malicious requests using the pattern .%00.../.%00.../ which effectively circumvents the plugin's security measures by injecting null bytes that terminate the string processing before the traversal characters are properly trimmed. This technique exploits a fundamental weakness in the input sanitization process where the application does not properly validate or sanitize the input before processing, allowing malicious payloads to persist through the filtering mechanism. The attack vector specifically targets the plugin's image optimization and caching functionality, where it processes file paths and attempts to resolve file locations on the server. The vulnerability can be leveraged to access sensitive files on the server, potentially including configuration files, database credentials, and other system information that could be used for further compromise.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to gain unauthorized access to the WordPress installation and potentially escalate privileges within the system. Successful exploitation allows an attacker to retrieve arbitrary files from the server, which could include sensitive configuration data, user credentials, or other confidential information stored in the application's file structure. The vulnerability is particularly dangerous because it can be exploited by unauthenticated users, meaning that anyone with access to the affected WordPress site can attempt to exploit this weakness without requiring valid credentials. This makes the attack surface significantly larger and increases the likelihood of successful exploitation. The vulnerability also poses risks to the overall integrity of the WordPress installation, as it can potentially be used to upload malicious files or modify existing components, leading to persistent backdoors or complete system compromise.
Mitigation strategies for this vulnerability should focus on immediate patching of the WP Rocket plugin to version 2.9.4 or later, which contains proper input validation and sanitization mechanisms that address the null byte bypass techniques. Organizations should also implement network-level protections such as web application firewalls that can detect and block suspicious null byte sequences in URL parameters. The recommended approach includes comprehensive input validation that treats all null bytes as invalid characters and implements proper encoding checks that prevent the exploitation of character encoding vulnerabilities. Additionally, system administrators should conduct thorough security audits of all WordPress plugins and themes to identify similar vulnerabilities in other components of the application stack. The implementation of proper logging and monitoring mechanisms can help detect exploitation attempts and provide early warning of potential attacks. Organizations should also consider implementing principle of least privilege access controls and regular security assessments to prevent similar vulnerabilities from being introduced through third-party components in their web applications. This vulnerability demonstrates the importance of robust input validation and the dangers of relying on simplistic security measures that can be easily bypassed through advanced exploitation techniques.