CVE-2020-17449 in php-fusion
Summary
by MITRE
PHP-Fusion 9.03 allows XSS via the error_log file.
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Analysis
by VulDB Data Team • 08/13/2020
The vulnerability CVE-2020-17449 represents a cross-site scripting flaw within PHP-Fusion version 9.03 that specifically targets the error_log file handling mechanism. This issue arises from inadequate input sanitization and output encoding practices within the content management system's error reporting functionality. The vulnerability stems from the application's failure to properly escape or filter user-controllable data that gets written to and subsequently displayed from the error_log file, creating an avenue for malicious actors to inject persistent script code into the application's error handling mechanisms.
The technical exploitation of this vulnerability occurs when user-supplied input containing malicious script code is processed by the PHP-Fusion application and subsequently logged to the error_log file. When administrators or users view error logs through the web interface, the unescaped script code gets executed in the browser context of the victim user. This represents a classic persistent cross-site scripting attack vector where the malicious payload is stored server-side in the error_log file and then served to users without proper sanitization. The vulnerability is categorized under CWE-79 as it involves the improper sanitization of user-controllable data in web applications, specifically within error handling components.
The operational impact of CVE-2020-17449 extends beyond simple script injection, as it enables attackers to potentially hijack user sessions, steal sensitive information, or redirect victims to malicious domains. An attacker could craft specially formatted input that, when processed by the application, would generate error messages containing malicious JavaScript payloads. These payloads would then be executed whenever legitimate users view the error logs, potentially leading to complete compromise of user accounts and unauthorized access to sensitive administrative functions. The vulnerability is particularly concerning because it operates through the error logging mechanism, which is typically overlooked during security assessments and may not be properly monitored for malicious content.
Mitigation strategies for this vulnerability require immediate implementation of proper input validation and output encoding throughout the PHP-Fusion application, particularly within error handling and logging components. Organizations should implement comprehensive sanitization of all user-controllable data before it is processed or logged, ensuring that special characters are properly escaped before being written to the error_log file. The recommended approach includes implementing context-specific output encoding, where data is encoded appropriately based on the target execution context such as HTML, JavaScript, or URL contexts. Additionally, access controls should be strengthened for error_log files, limiting administrative access and implementing proper file permissions to prevent unauthorized modification or viewing of sensitive log data. Security monitoring should include regular scanning of log files for suspicious content and implementation of web application firewalls to detect and block malicious payloads. The remediation efforts should align with ATT&CK technique T1566 for credential access through malicious file content and T1059 for command and script injection through persistent script execution mechanisms.