CVE-2022-2102 in SEPCOS
Summary
by MITRE • 06/24/2022
Controls limiting uploads to certain file extensions may be bypassed. This could allow an attacker to intercept the initial file upload page response and modify the associated code. This modified code can be forwarded and used by a script loaded later in the sequence, allowing for arbitrary file upload into a location where PHP scripts may be executed.
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Analysis
by VulDB Data Team • 07/14/2022
The vulnerability identified as CVE-2022-2102 represents a critical security flaw in web application file upload controls that directly impacts the integrity of server-side validation mechanisms. This issue stems from insufficient client-side and server-side validation of file extensions, creating a pathway for attackers to circumvent intended security restrictions. The vulnerability specifically targets applications that implement controls to limit file uploads to specific extensions, typically to prevent the execution of malicious code. When these controls are bypassed, attackers can potentially upload files with extensions that would normally be restricted, leading to potential code execution on the server. The flaw operates through a sophisticated manipulation of the upload process where an attacker intercepts the initial file upload page response and modifies the associated client-side code. This modification allows the attacker to alter the file type validation logic, effectively creating a backdoor for arbitrary file uploads that can be executed in contexts where PHP scripts are processed. The vulnerability demonstrates a fundamental weakness in the application's defense-in-depth strategy, where client-side validation is insufficient to prevent malicious activities.
The technical implementation of this vulnerability leverages the principle of client-side trust and the assumption that client-side validation can be relied upon for security purposes. The flaw exploits the fact that many applications implement client-side validation as a first line of defense, assuming that users cannot modify the client-side code or that such modifications would be detected. However, attackers can intercept the initial page response and modify the JavaScript or HTML elements that control file upload behavior. This modification can involve changing the accepted file types, removing validation checks, or altering the upload parameters to include executable file types. The modified code is then forwarded to a script that executes later in the application sequence, creating a persistent mechanism for file upload bypass. This approach aligns with common attack patterns documented in the attack tactics and techniques framework, particularly those related to command and control operations and privilege escalation through file manipulation. The vulnerability specifically relates to CWE-434, which addresses insecure file upload handling, and can be categorized under the broader ATT&CK tactic of Execution through the ability to run arbitrary code on the server.
The operational impact of CVE-2022-2102 extends far beyond simple file upload bypass, as it creates a persistent threat vector that can lead to complete system compromise. When attackers successfully exploit this vulnerability, they can upload malicious PHP scripts or other executable files to directories where the web server has execution privileges. This capability allows for remote code execution, enabling attackers to establish persistent access, exfiltrate data, or deploy additional malware. The vulnerability can be exploited through various attack vectors including social engineering to manipulate users into interacting with modified upload pages, or through automated tools that can intercept and modify responses in real-time. The implications are particularly severe in web applications that process user-uploaded content, such as content management systems, file sharing platforms, or any application that allows users to upload files to the server. The attack can be executed without requiring elevated privileges on the client side, making it accessible to threat actors with limited technical expertise. Organizations may not immediately detect this type of attack as it can appear as legitimate file uploads, especially when the malicious files are disguised as common file types. The vulnerability also demonstrates poor separation of concerns in application security, where the trust boundary between client and server is incorrectly assumed to be sufficient for security enforcement. This flaw can result in data breaches, system compromise, and potential regulatory violations depending on the nature of the data processed by the affected applications.
Mitigation strategies for CVE-2022-2102 require a comprehensive approach that addresses both client-side and server-side validation mechanisms while implementing robust security controls. Organizations should implement server-side file validation that is independent of client-side controls, ensuring that file type checking occurs on the server before any file processing begins. This includes validating file content using multiple methods such as MIME type detection, file signature analysis, and extension validation against a strict whitelist of approved file types. The implementation should include proper input sanitization and the use of secure file storage mechanisms that prevent execution of uploaded files in web-accessible directories. Additionally, organizations should implement proper access controls and file permissions that prevent uploaded files from being executed in contexts where they could cause harm. The solution must also include monitoring and logging of file upload activities to detect anomalous behavior or attempts to exploit the vulnerability. Security measures should be integrated with proper application architecture principles that separate the trust boundaries between client and server, ensuring that server-side validation cannot be bypassed through client-side modifications. This vulnerability highlights the importance of following security best practices outlined in industry standards such as the OWASP Top Ten and NIST cybersecurity frameworks, particularly in areas related to input validation, secure coding practices, and defense-in-depth strategies. Regular security testing including penetration testing and code reviews should be conducted to identify and remediate similar vulnerabilities in the application codebase.