Unrestricted File Upload lead to RCE Expose Database Information
- What is Unrestricted File Upload?
Unrestricted File Upload (UFU) vulnerability refers to a security issue in web applications where an attacker can upload files of any type to the server without proper validation or controls. This can have serious consequences, especially if the uploaded files contain malicious content, such as scripts or executable code.
The lack of proper validation allows attackers to bypass restrictions on file uploads, potentially leading to various security threats.
- What is RCE (Remote Code Execution)?
Remote Code Execution (RCE) is a security vulnerability that occurs when an attacker can execute arbitrary code on a target system or application from a remote location. This type of vulnerability poses a significant threat because it allows attackers to take control of a system or server, potentially leading to unauthorized access, data breaches, and other malicious activities.
Then if attacker can combine both of the attack, it’s would be terrifying for the target / victim. Because, the Unrestricted File Upload (UFU) vulnerabilities can lead to Remote Code Execution (RCE) when an application or website allows users to upload files without proper validation and controls.
Attack Vector
The hacker can insert harmful code by inputting a semicolon along with the payload. This semicolon causes the eval function to interpret the rest of the payload as if it were a fresh instruction within PHP.
http://www.vulnerable.com/dashboard.php?user=true;phpinfo();
the result will be:
echo true;
phpinfo();
Risk Factor
1. The vulnerability has a significant impact, as potential code can be executed either in the server context or on the client side. The likelihood of detection by the attacker is high, and the prevalence of this vulnerability is common, resulting in a high severity level. It is crucial to thoroughly assess a file upload module’s access controls to properly analyze the associated risks.
2. The vulnerability has a significant impact, as potential code can be executed either in the server context or on the client side. The likelihood of detection by the attacker is high, and the prevalence of this vulnerability is common, resulting in a high severity level. It is crucial to thoroughly assess a file upload module’s access controls to properly analyze the associated risks.
3. Regarding server-side attacks, compromising the web server is possible through the upload and execution of a web shell. This web shell can perform various actions, including running commands, browsing system files, accessing local resources, attacking other servers, and exploiting local vulnerabilities. On the client side, uploading malicious files can expose the website to client-side attacks like XSS or Cross-site Content Hijacking.
4. Uploaded files may be exploited to target other vulnerable sections of an application, potentially leading to both client-side and server-side attacks. Vulnerabilities in broken libraries or applications on either the client or server side can be triggered by uploaded files, exemplified by instances such as the ImageMagick flaw known as ImageTragick or the Symantec antivirus exploit through unpacking a RAR file.
5. Malicious files, including Unix shell scripts, Windows viruses, Excel files with dangerous formulas, or reverse shells, could be uploaded to the server. This allows for code execution by an administrator or webmaster later, potentially compromising the victim’s machine. Attackers might also use this vulnerability to insert phishing pages into the website or deface the site.
6. The file storage server itself might be misused to host problematic files, including malware, illegal software, or adult content. Uploaded files could also contain command and control data for malware, violent and harassing messages, or steganographic data that criminal organizations may utilize. Additionally, sensitive files uploaded may be accessible by unauthorized individuals. File uploaders may inadvertently disclose internal information, such as server internal paths, in their error messages.
- Action to Produce PoC
Disclaimer: Writer already cover up the domain, credential data & etc..
- Conclusion
To mitigate the risk of Unrestricted File Upload vulnerabilities leading to Remote Code Execution (RCE), implement rigorous file type and content validation, enforce strict size limits, and employ whitelisting for allowed file types.
Additionally, regularly update and patch the application, secure file storage with restricted access, and conduct thorough security audits to identify and address potential weaknesses in the file upload functionality.
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