CVE-2019-9858 in Groupware Webmail Edition
Summary
by MITRE
Remote code execution was discovered in Horde Groupware Webmail 5.2.22 and 5.2.17. Horde/Form/Type.php contains a vulnerable class that handles image upload in forms. When the Horde_Form_Type_image method onSubmit() is called on uploads, it invokes the functions getImage() and _getUpload(), which uses unsanitized user input as a path to save the image. The unsanitized POST parameter object[photo][img][file] is saved in the $upload[img][file] PHP variable, allowing an attacker to manipulate the $tmp_file passed to move_uploaded_file() to save the uploaded file. By setting the parameter to (for example) ../usr/share/horde/static/bd.php, one can write a PHP backdoor inside the web root. The static/ destination folder is a good candidate to drop the backdoor because it is always writable in Horde installations. (The unsanitized POST parameter went probably unnoticed because it's never submitted by the forms, which default to securely using a random path.)
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Analysis
by VulDB Data Team • 06/26/2024
CVE-2019-9858 represents a critical remote code execution vulnerability affecting Horde Groupware Webmail versions 5.2.17 and 5.2.22. This vulnerability resides within the Horde/Form/Type.php file where a vulnerable class handles image upload functionality in web forms. The flaw manifests when the Horde_Form_Type_image method's onSubmit() function processes user uploads, specifically invoking getImage() and _getUpload() functions that utilize unsanitized user input as file path parameters. The vulnerability stems from the improper handling of the POST parameter object[photo][img][file] which gets directly assigned to the $upload[img][file] PHP variable without adequate validation or sanitization. This unsanitized input subsequently influences the $tmp_file variable that gets passed to the move_uploaded_file() function, creating a path traversal condition that allows arbitrary file placement within the web root directory.
The technical exploitation of this vulnerability follows a specific attack pattern that leverages the predictable writable nature of the static/ directory within Horde installations. Attackers can manipulate the malicious POST parameter to specify paths such as ../usr/share/horde/static/bd.php, effectively bypassing normal file upload restrictions and enabling the placement of PHP backdoor files directly within the web accessible directory structure. This path traversal vulnerability is particularly dangerous because it allows attackers to write executable PHP code directly into the web root where it can be executed by the web server, providing persistent access to the compromised system. The vulnerability's stealth is enhanced by the fact that the malicious parameter is not typically submitted through normal form operations, making it less likely to be detected during routine security monitoring or input validation checks.
The operational impact of CVE-2019-9858 extends far beyond simple unauthorized file placement, as it provides attackers with complete remote code execution capabilities on affected systems. Once a malicious PHP backdoor is successfully uploaded, attackers can execute arbitrary commands on the target server, potentially escalating privileges, establishing persistent access, or using the compromised system as a launch point for further attacks within the network. This vulnerability directly maps to CWE-22 Path Traversal and CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component, both of which are classified as high-risk issues in the Common Weakness Enumeration catalog. The attack vector aligns with ATT&CK technique T1105 Command and Scripting Interpreter, specifically focusing on the execution of malicious code through web-based attack surfaces.
Organizations affected by this vulnerability should immediately implement multiple layers of mitigation strategies to protect their systems. The most critical immediate action involves applying the vendor-provided security patches and updates to upgrade to versions that address this specific path traversal flaw. Additionally, implementing proper input validation and sanitization measures for all user-supplied data, particularly file upload parameters, is essential to prevent similar vulnerabilities from occurring in the future. Network-based protections such as web application firewalls should be configured to monitor for suspicious file upload patterns and path traversal attempts. Regular security auditing of file upload functionality, combined with proper access controls and directory permissions, will help prevent unauthorized file placement in web-accessible directories. The vulnerability also highlights the importance of Principle of Least Privilege implementation, ensuring that web server processes operate with minimal required permissions to limit potential damage from successful exploitation attempts.