CVE-2018-19370 in Yoast SEO Plugin
Summary
by MITRE
A Race condition vulnerability in unzip_file in admin/import/class-import-settings.php in the Yoast SEO (wordpress-seo) plugin before 9.2.0 for WordPress allows an SEO Manager to perform command execution on the Operating System via a ZIP import.
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Analysis
by VulDB Data Team • 06/12/2023
The vulnerability identified as CVE-2018-19370 represents a critical race condition flaw within the Yoast SEO WordPress plugin that affects versions prior to 9.2.0. This issue resides in the unzip_file function located in admin/import/class-import-settings.php, where the plugin fails to properly validate file extraction operations during import processes. The race condition occurs when the system processes compressed files containing malicious payloads, creating a window of opportunity for unauthorized command execution on the underlying operating system. Attackers exploiting this vulnerability can manipulate the import mechanism to execute arbitrary commands with the privileges of the web server process, potentially leading to complete system compromise.
The technical exploitation of this vulnerability stems from improper handling of temporary file operations during ZIP decompression. When the plugin imports settings from a ZIP archive, it creates temporary files in predictable locations without adequate synchronization mechanisms to prevent concurrent access. This race condition allows an attacker to substitute the intended archive content with malicious files, particularly focusing on creating symbolic links or modifying file permissions during the extraction process. The flaw aligns with CWE-367, which categorizes time-of-check to time-of-use vulnerabilities, where the system's validation occurs at a different moment than the actual execution. This timing discrepancy enables attackers to manipulate the environment between validation and execution phases, ultimately enabling arbitrary code execution capabilities.
From an operational perspective, this vulnerability poses significant risks to WordPress installations using the affected Yoast SEO plugin versions. An attacker with access to the SEO Manager role can leverage this weakness to execute commands on the target system, potentially escalating privileges, installing backdoors, or exfiltrating sensitive data. The impact extends beyond individual site compromise, as compromised WordPress installations often serve as entry points for broader network infiltration. The vulnerability affects the principle of least privilege, as the attacker's access level of SEO Manager is sufficient to achieve system-level command execution, bypassing typical security boundaries that would normally protect against such attacks. This weakness can be particularly dangerous in multi-site environments where a single compromised installation may affect the entire network infrastructure.
Organizations should immediately update their Yoast SEO plugin to version 9.2.0 or later to remediate this vulnerability, as no effective workarounds exist for the race condition itself. The mitigation strategy must include comprehensive monitoring of import activities and file system changes during plugin operations, particularly focusing on temporary file creation and modification patterns. Security teams should implement network-based intrusion detection systems to monitor for suspicious command execution patterns that may indicate exploitation attempts. Additionally, implementing strict file permission controls and restricting write access to plugin directories can limit the impact of potential exploitation. The vulnerability demonstrates the critical importance of proper input validation and file handling procedures in web applications, aligning with ATT&CK technique T1059 for command and script injection, where attackers leverage application weaknesses to execute malicious commands through legitimate system interfaces. Organizations should also consider implementing automated patch management processes to ensure timely application of security updates, particularly for widely-used plugins that handle user-supplied data.