CVE-2020-36898

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CVE-2020-36898 QiHang Media Web Digital Signage unauthenticated file deletion directory traversal critical vulnerability security advisory vulnerability database remote code execution

Summary

CVE-2020-36898 is a critical severity vulnerability affecting QiHang Media Web Digital Signage 3.0.9. It allows unauthenticated remote attackers to delete arbitrary files on the server via directory traversal in the QH.aspx endpoint, potentially leading to significant data loss and system compromise.

Technical Details

CVE-2020-36898 arises from a lack of proper input validation in the QH.aspx endpoint of QiHang Media Web Digital Signage 3.0.9. Specifically, the data parameter, which is intended to specify the file to be processed, is vulnerable to directory traversal attacks. An attacker can craft a malicious POST request to QH.aspx with a data parameter containing directory traversal sequences (e.g., ../) to navigate the file system and delete files outside of the intended directory. Because the endpoint does not require authentication, any attacker with network access to the server can exploit this vulnerability. The web server's permissions are used to delete the files, which could lead to the deletion of critical system files if the web server has elevated privileges.

The vulnerability resides in the insufficient sanitization of user-supplied input before it's used to construct file paths. This allows attackers to bypass intended security restrictions and manipulate the file system in unintended ways.

Affected Products and Versions

  • howfor qihang_media_web_digital_signage 3.0.9

Impact Assessment

Successful exploitation of CVE-2020-36898 can have severe consequences, including:

  • Arbitrary File Deletion: Attackers can delete any file accessible to the web server user, leading to data loss and system instability.
  • System Compromise: Deletion of critical system files can render the system unusable.
  • Denial of Service (DoS): By deleting essential files, attackers can effectively shut down the digital signage system.
  • Data Breach Risk: While primarily a file deletion vulnerability, the ability to manipulate the file system could potentially be chained with other vulnerabilities to exfiltrate sensitive data.

Remediation

Immediate Actions

  • Restrict Network Access: Limit access to the QiHang Media Web Digital Signage server to only authorized users and networks.
  • Monitor System Logs: Closely monitor system logs for suspicious activity, particularly requests to the QH.aspx endpoint with directory traversal sequences.
  • Implement a Web Application Firewall (WAF): Deploy a WAF to filter malicious requests and block directory traversal attempts.

Long-term Solutions

  • Apply Patch/Upgrade: Contact the vendor (howfor) for a security patch or upgrade to a version that addresses this vulnerability. If a patch is unavailable, consider migrating to a more secure digital signage solution.
  • Input Validation: Implement robust input validation on the data parameter in the QH.aspx endpoint to prevent directory traversal attacks. Sanitize and validate all user-supplied input before using it to construct file paths.
  • Least Privilege Principle: Ensure that the web server user has the minimum necessary privileges to perform its required tasks. Avoid running the web server with root or administrator privileges.

References

Detection & Scanning

This vulnerability can be detected by monitoring network traffic for POST requests to the QH.aspx endpoint containing directory traversal sequences (e.g., ../) in the data parameter. Security scanners and penetration testing tools can also be used to identify this vulnerability.

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