CVE-2020-5620 in Exment
Summary
by MITRE
Cross-site scripting vulnerability in Exment prior to v3.6.0 allows remote authenticated attackers to inject arbitrary script or HTML via a specially crafted file.
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Analysis
by VulDB Data Team • 08/25/2020
The vulnerability identified as CVE-2020-5620 represents a critical cross-site scripting flaw within the Exment application platform, specifically affecting versions prior to v3.6.0. This vulnerability resides in the application's handling of file uploads and processing mechanisms, creating a pathway for malicious actors to execute arbitrary code within the context of affected user sessions. The flaw manifests when the system processes specially crafted files that contain malicious script payloads, which are then rendered in web interfaces without proper sanitization or validation. Attackers exploiting this vulnerability can manipulate the application's behavior to execute unauthorized scripts, potentially leading to complete session hijacking, data exfiltration, or further compromise of the affected systems.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within Exment's file processing pipeline. When authenticated users interact with the application's file upload functionality, the system fails to adequately sanitize file contents or metadata, allowing malicious payloads to persist within the application's data stores. This weakness specifically affects the application's ability to distinguish between legitimate user content and potentially harmful script code, creating an environment where attackers can embed malicious javascript or html code within file names, descriptions, or content attributes. The vulnerability is classified under CWE-79 as a failure to sanitize user input, which directly enables XSS attacks. The attack surface is expanded through the authentication requirement, as attackers must first establish valid credentials to exploit this weakness, though this does not prevent the execution of malicious payloads once access is obtained.
The operational impact of CVE-2020-5620 extends beyond simple script injection, as it provides attackers with the capability to manipulate user sessions and potentially escalate privileges within the application. When successfully exploited, the vulnerability allows attackers to execute arbitrary scripts in the context of other users' browsers, potentially leading to unauthorized data access, modification, or deletion. The authenticated nature of the attack means that attackers can leverage existing user permissions and roles within the application, potentially accessing sensitive information or performing actions that would otherwise be restricted. This vulnerability can be particularly dangerous in enterprise environments where Exment applications may contain sensitive business data, employee information, or proprietary assets. The impact is further amplified by the fact that the vulnerability affects the file handling capabilities, which are commonly used in business applications for document management, data import/export, and content sharing operations.
Mitigation strategies for CVE-2020-5620 primarily focus on upgrading to Exment version 3.6.0 or later, which includes proper input validation and sanitization measures for file processing. Organizations should implement comprehensive file validation mechanisms that inspect file contents, metadata, and naming conventions to prevent malicious payloads from being accepted. Network segmentation and access controls should be enforced to limit the potential impact of successful exploitation attempts. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities within the application ecosystem. The remediation process should include thorough code reviews focusing on input validation, output encoding, and file handling procedures. Security teams should also implement web application firewalls and content security policies to provide additional layers of protection against XSS attacks. According to ATT&CK framework, this vulnerability maps to T1566.001 (Phishing with Malicious File) and T1059.007 (Command and Scripting Interpreter: JavaScript), emphasizing the need for both user education and technical controls to prevent exploitation. Organizations should also consider implementing automated monitoring solutions that can detect anomalous file upload activities and potential XSS payload delivery attempts.