CVE-2018-7771 in U.motion Builder
Summary
by MITRE
The vulnerability exists within processing of editscript.php in Schneider Electric U.motion Builder software versions prior to v1.3.4. A directory traversal vulnerability allows a caller with standard user privileges to write arbitrary php files anywhere in the web service directory tree.
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Analysis
by VulDB Data Team • 02/24/2020
The vulnerability identified as CVE-2018-7771 resides within Schneider Electric U.motion Builder software, specifically in the editscript.php component affecting versions prior to v1.3.4. This directory traversal flaw represents a critical security weakness that undermines the integrity of the web service infrastructure by permitting unauthorized file operations. The vulnerability manifests when the application processes user-supplied input without adequate validation or sanitization, creating an exploitable path that bypasses normal access controls and directory restrictions. Such a flaw fundamentally compromises the application's ability to maintain proper file system boundaries and access controls.
The technical implementation of this vulnerability stems from improper input validation within the editscript.php handler, which fails to adequately sanitize user-provided parameters that influence file path construction. When legitimate users submit edit requests through the web interface, the application constructs file paths based on these inputs without sufficient verification of directory traversal sequences or absolute path references. This processing error creates an opportunity for attackers to manipulate the file system operations by inserting malicious path components such as ../ or ..\ sequences that navigate outside the intended web root directory. The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as directory traversal or path traversal attacks. The flaw operates at the intersection of input validation and file system access control mechanisms, where insufficient sanitization allows arbitrary file operations to occur within the web service directory tree.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass full system compromise capabilities for attackers with standard user privileges. An attacker can leverage this weakness to write arbitrary PHP files anywhere within the web service directory structure, potentially creating backdoor access points, injecting malicious code, or establishing persistent access mechanisms. This capability enables attackers to bypass normal authentication and authorization controls, effectively elevating their privileges to those of the web service account. The vulnerability creates a persistent threat vector that can be exploited repeatedly, as the attacker can place malicious payloads in locations that will be executed by the web server. The consequences include potential data exfiltration, system compromise, and disruption of industrial control processes that rely on the affected software for operation. This type of vulnerability particularly impacts industrial environments where Schneider Electric U.motion Builder is deployed for building automation and control system management.
Mitigation strategies for CVE-2018-7771 require immediate implementation of software updates to version 1.3.4 or later, which contain the necessary patches to address the directory traversal vulnerability. Organizations should also implement network segmentation and access controls to limit exposure of the affected web service to unauthorized users, applying the principle of least privilege to reduce potential attack surface. Input validation should be strengthened through proper parameter sanitization and path normalization techniques that prevent directory traversal sequences from being processed. Additionally, security monitoring should be enhanced to detect unusual file creation patterns or unauthorized modifications to web service directories. The vulnerability demonstrates the importance of proper secure coding practices and input validation, particularly in industrial control systems where security is paramount. Organizations should conduct thorough vulnerability assessments to identify similar weaknesses in other components of their industrial control infrastructure and apply comprehensive security hardening measures to protect against similar threats. This vulnerability also highlights the need for regular security updates and patch management processes in industrial environments where legacy systems may be vulnerable to exploitation.