CVE-2020-10557 in AContent
Summary
by MITRE
An issue was discovered in AContent through 1.4. It allows the user to run commands on the server with a low-privileged account. The upload section in the file manager page contains an arbitrary file upload vulnerability via upload.php. The extension .php7 bypasses file upload restrictions.
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Analysis
by VulDB Data Team • 04/16/2024
The vulnerability identified as CVE-2020-10557 represents a critical arbitrary file upload flaw within AContent version 1.4 and earlier, exposing systems to remote command execution risks. This vulnerability specifically targets the file manager component of the application where users can upload files through the upload.php endpoint. The flaw stems from inadequate input validation and file extension filtering mechanisms that fail to properly restrict malicious file uploads, creating a pathway for attackers to execute arbitrary code on the target server. The vulnerability is particularly concerning because it allows execution with a low-privileged account, which can serve as a foothold for further escalation within the system environment.
The technical exploitation of this vulnerability occurs through the bypass of file upload restrictions using the .php7 file extension, which demonstrates a weakness in the application's file type validation logic. This bypass technique exploits the fact that the application's security controls do not adequately filter or validate file extensions, allowing attackers to upload malicious PHP files with extensions that are not properly blocked. The .php7 extension specifically circumvents standard security measures that typically block .php files, enabling attackers to execute malicious code on the server with the privileges of the web application user. This represents a classic case of insecure file upload handling that can lead to complete system compromise when combined with other attack vectors.
The operational impact of CVE-2020-10557 extends beyond simple code execution, as it can enable attackers to establish persistent access, escalate privileges, and potentially compromise the entire application infrastructure. Once an attacker successfully uploads a malicious file, they can leverage the low-privileged account to perform reconnaissance, establish backdoors, and potentially move laterally within the network. This vulnerability aligns with CWE-434 which identifies insecure file upload vulnerabilities, and maps to ATT&CK techniques including T1105 for remote file execution and T1059 for command and script injection. The vulnerability can be particularly dangerous in environments where AContent is used for content management, as it provides attackers with direct access to server resources and potentially sensitive data stored within the application.
Mitigation strategies for CVE-2020-10557 should focus on implementing robust input validation, proper file extension filtering, and secure file handling practices. Organizations should immediately upgrade to AContent version 1.5 or later where this vulnerability has been addressed through enhanced file upload restrictions and improved validation mechanisms. Additional defensive measures include implementing proper file type checking using multiple validation methods, such as content-based verification alongside extension checks, and ensuring that uploaded files are stored outside the web root directory. Network-level protections such as web application firewalls should be configured to monitor and block suspicious upload attempts, while regular security audits should verify that file upload functionality properly enforces access controls and sanitizes all user inputs. The vulnerability demonstrates the critical importance of defense-in-depth strategies and proper access control implementation to prevent unauthorized code execution in web applications.