CVE-2021-3199 in Document Server
Summary
by MITRE • 01/26/2021
Directory traversal with remote code execution can occur in /upload in ONLYOFFICE Document Server before 5.6.3, when JWT is used, via a /.. sequence in an image upload parameter.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 02/20/2021
The vulnerability described in CVE-2021-3199 represents a critical directory traversal flaw within the ONLYOFFICE Document Server software that can be exploited to achieve remote code execution. This vulnerability specifically affects versions prior to 5.6.3 and occurs during the image upload process through the /upload endpoint when the system employs JSON Web Token authentication mechanisms. The flaw stems from inadequate input validation and path sanitization within the file upload handling logic, allowing malicious actors to manipulate file paths through the use of directory traversal sequences.
The technical implementation of this vulnerability involves the exploitation of a /.. sequence within the image upload parameter, which enables attackers to navigate outside the intended upload directory and potentially write files to arbitrary locations on the server filesystem. This type of vulnerability falls under the Common Weakness Enumeration category CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as directory traversal or path traversal attacks. The vulnerability is particularly dangerous because it combines path traversal with remote code execution capabilities, allowing attackers to not only access restricted files but also to execute arbitrary code on the target system.
The operational impact of CVE-2021-3199 is severe and multifaceted, affecting organizations that rely on ONLYOFFICE Document Server for document management and collaboration services. Attackers can leverage this vulnerability to upload malicious files, potentially including web shells or other malicious executables, which can then be executed to gain full control over the affected server. This compromise can lead to data exfiltration, system infiltration, and further lateral movement within the network. The vulnerability is particularly concerning in environments where the Document Server is exposed to untrusted networks or where JWT authentication is implemented without proper additional security controls. Organizations may face significant regulatory and compliance implications, especially in industries governed by standards such as SOC 2, ISO 27001, or HIPAA, where such vulnerabilities can result in audit failures and mandatory security remediation requirements.
The exploitation of this vulnerability aligns with tactics described in the MITRE ATT&CK framework, specifically under the T1059.007 technique for command and script injection, as well as T1078.004 for valid accounts, since the JWT authentication mechanism may be leveraged to establish initial access. The vulnerability also relates to T1566 for initial access through the exploitation of web application vulnerabilities. Organizations should implement immediate mitigations including updating to version 5.6.3 or later, which contains proper input validation and path sanitization measures. Additional protective measures include implementing proper network segmentation, restricting access to the upload endpoints, and deploying web application firewalls to monitor and block suspicious path traversal patterns. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other applications and systems within the organization's infrastructure.