CVE-2018-11340 in AS6202T ADM
Summary
by MITRE
An unrestricted file upload vulnerability in importuser.cgi in ASUSTOR AS6202T ADM 3.1.0.RFQ3 allows attackers to upload supplied data to a specified filename. This can be used to place attacker controlled code on the file system that is then executed.
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Analysis
by VulDB Data Team • 02/07/2020
The vulnerability identified as CVE-2018-11340 represents a critical unrestricted file upload flaw in the ASUSTOR AS6202T ADM 3.1.0.RFQ3 system management interface. This vulnerability exists within the importuser.cgi script which processes user import functionality, creating a pathway for remote attackers to execute arbitrary code on the affected system. The flaw stems from inadequate input validation and sanitization mechanisms that fail to properly verify the file type and content before storing uploaded files to the server's filesystem. According to CWE-434, this vulnerability maps directly to unrestricted file upload issues where the application accepts files without proper restrictions on file type or content, making it susceptible to malicious file injection attacks.
The technical exploitation of this vulnerability occurs when an attacker uploads a specially crafted file through the importuser.cgi endpoint, which then gets stored with a predictable or attacker-controlled filename. This allows the malicious file to be executed within the context of the web server, potentially granting the attacker full control over the affected system. The vulnerability's impact is particularly severe because it enables remote code execution without requiring authentication, as the upload functionality is accessible to unauthenticated users. The attack chain typically involves uploading a web shell or malicious script that can then be executed through subsequent HTTP requests, providing persistent access to the system. This represents a classic example of CWE-20, which describes improper input validation, where the system fails to properly validate and sanitize user-supplied data before processing it.
The operational impact of CVE-2018-11340 extends beyond immediate system compromise, as it provides attackers with a foothold for further reconnaissance and lateral movement within network environments. Once executed, the uploaded malicious code can be used to establish reverse shells, download additional payloads, or scan internal network resources for additional vulnerable systems. The vulnerability's persistence is enhanced by the fact that the uploaded files remain on the filesystem and can be executed repeatedly without requiring re-upload, making it particularly dangerous for long-term attacks. Organizations using ASUSTOR ADM systems may face complete system compromise, data exfiltration, and potential use as a launchpad for broader network attacks. The vulnerability aligns with ATT&CK technique T1190, which covers exploiting vulnerabilities in web applications, and T1059, which covers command and scripting interpreter usage, as attackers can leverage the uploaded code to execute system commands and maintain persistence.
Mitigation strategies for this vulnerability should include immediate implementation of file type restrictions and content validation for all upload endpoints, ensuring that only safe file types are accepted. The system should enforce strict file extension checks and validate file contents against known good signatures to prevent malicious files from being uploaded. Network segmentation and firewall rules should be implemented to restrict access to administrative interfaces, while regular security audits should monitor for unauthorized file uploads. Additionally, implementing web application firewalls and intrusion detection systems can help detect and block malicious upload attempts. The affected ASUSTOR ADM 3.1.0.RFQ3 version should be updated to the latest available patch release that addresses this vulnerability, as manufacturers typically release security updates to remediate such flaws. Organizations should also implement proper monitoring of system logs for suspicious file upload activities and establish incident response procedures to quickly address potential exploitation attempts.