CVE-2019-6726 in WP Fastest Cache Plugin
Summary
by MITRE
The WP Fastest Cache plugin through 0.8.9.0 for WordPress allows remote attackers to delete arbitrary files because wp_postratings_clear_fastest_cache and rm_folder_recursively in wpFastestCache.php mishandle ../ in an HTTP Referer header.
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Analysis
by VulDB Data Team • 06/13/2024
The vulnerability identified as CVE-2019-6726 affects the WP Fastest Cache plugin version 0.8.9.0 and earlier, presenting a critical file deletion risk within WordPress environments. This issue stems from improper handling of directory traversal sequences in HTTP Referer headers, specifically the ../ pattern that allows attackers to manipulate file paths beyond intended boundaries. The vulnerability resides in two primary functions within the wpFastestCache.php file: wp_postratings_clear_fastest_cache and rm_folder_recursively, which fail to properly sanitize user-supplied input from the Referer header. This flaw enables remote attackers to execute unauthorized file deletion operations on the affected WordPress installation, potentially compromising the entire web application and underlying server infrastructure.
The technical exploitation of this vulnerability occurs through manipulation of the HTTP Referer header to include directory traversal sequences that bypass normal path validation mechanisms. When the vulnerable plugin processes requests containing specially crafted ../ sequences in the Referer header, it incorrectly interprets these patterns as legitimate directory navigation commands. This misinterpretation leads to the execution of file deletion operations against arbitrary paths on the server filesystem, potentially allowing attackers to remove critical application files, configuration data, or even system files depending on the server permissions. The vulnerability demonstrates characteristics of CWE-22 - Improper Limitation of a Pathname to a Restricted Directory, which specifically addresses insufficient validation of file paths and directory traversal attacks.
The operational impact of this vulnerability extends beyond simple file deletion capabilities, as it represents a severe privilege escalation vector that can lead to complete system compromise. Attackers can leverage this weakness to remove core WordPress files, plugin components, or even the entire WordPress installation, effectively rendering the website inaccessible and potentially providing a foothold for further attacks. The vulnerability also poses significant risks to data integrity and availability, as it allows unauthorized deletion of cached content, user data, or system configuration files that may be critical for normal operation. Additionally, the remote nature of this attack means that exploitation does not require local system access or authentication, making it particularly dangerous in environments where WordPress installations are publicly accessible.
Mitigation strategies for CVE-2019-6726 should prioritize immediate plugin updates to versions that address the directory traversal vulnerability, as the original developers have released patches to resolve this issue. System administrators should also implement web application firewall rules that monitor and filter HTTP Referer headers for suspicious directory traversal patterns, particularly those containing ../ sequences. Network-level protections can include implementing strict input validation at the perimeter and configuring server-side restrictions that prevent path traversal attacks from reaching the application layer. Security monitoring should focus on detecting unusual file deletion patterns and unauthorized access attempts to critical WordPress directories. Organizations should also consider implementing principle of least privilege configurations for WordPress file permissions, ensuring that web server processes cannot delete critical system files even if they manage to exploit this vulnerability. The ATT&CK framework categorizes this type of vulnerability under T1059 - Command and Scripting Interpreter and T1486 - Data Encrypted for Ransom, as the ability to delete arbitrary files can serve as a precursor to more sophisticated attacks including ransomware deployment or complete system compromise.