CVE-2020-28337 in Microweber
Summary
by MITRE • 02/16/2021
A directory traversal issue in the Utils/Unzip module in Microweber through 1.1.20 allows an authenticated attacker to gain remote code execution via the backup restore feature. To exploit the vulnerability, an attacker must have the credentials of an administrative user, upload a maliciously constructed ZIP file with file paths including relative paths (i.e., ../../), move this file into the backup directory, and execute a restore on this file.
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Analysis
by VulDB Data Team • 01/20/2025
The vulnerability identified as CVE-2020-28337 represents a critical directory traversal flaw within the Microweber content management platform version 1.1.20 and earlier. This security weakness exists specifically within the Utils/Unzip module and demonstrates how improper input validation can lead to severe remote code execution capabilities. The vulnerability requires an authenticated administrative user context to exploit, making it particularly dangerous as it leverages legitimate administrative privileges to bypass security controls. The attack vector specifically targets the backup restore functionality, which is a legitimate administrative feature designed for system recovery and data management.
The technical implementation of this vulnerability stems from inadequate sanitization of file paths during ZIP archive extraction processes. When the system processes a maliciously crafted ZIP file containing relative path traversal sequences such as ../../, the unzip utility fails to properly validate these paths before decompressing files. This allows an attacker to specify arbitrary file locations where extracted content should be placed, potentially overwriting critical system files or placing malicious code in execution paths. The vulnerability aligns with CWE-22 Directory Traversal and represents a classic example of insufficient input validation in file handling operations. The flaw operates at the file system level where the application does not properly restrict the destination paths of extracted files, creating a pathway for arbitrary file system modifications.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables full remote code execution capabilities. An attacker with administrative credentials can construct a malicious ZIP archive containing shell scripts or executable payloads that get deployed to critical system directories during the restore process. This compromise allows for persistent access, data exfiltration, system modification, and potential lateral movement within the network. The vulnerability's exploitation requires multiple steps including file upload, directory manipulation, and restore execution, which provides some operational complexity but also creates a clear attack chain that security teams can monitor for. The attack pattern follows established methodologies described in the MITRE ATT&CK framework under techniques such as T1059 Command and Scripting Interpreter and T1078 Valid Accounts, demonstrating how legitimate administrative functionality can be weaponized.
Mitigation strategies for CVE-2020-28337 should focus on immediate patching of affected Microweber installations to version 1.1.21 or later where the vulnerability has been addressed. Organizations should implement strict file validation mechanisms that sanitize all file paths during archive extraction processes, rejecting any paths containing directory traversal sequences. Network segmentation and privileged access controls should be enforced to limit administrative access to only authorized personnel, reducing the attack surface for this particular vulnerability. Additional defensive measures include monitoring backup directory activities, implementing file integrity checking mechanisms, and establishing automated scanning for malicious file patterns. The vulnerability serves as a reminder of the importance of input validation in file handling operations and demonstrates how seemingly benign administrative features can become attack vectors when proper security controls are not implemented. Organizations should also consider implementing web application firewalls and intrusion detection systems to monitor for suspicious file upload and restoration activities that could indicate exploitation attempts.