A critical arbitrary file write vulnerability in h2oai h2o-3 allows unauthenticated remote attackers to achieve remote code execution and gain full system control.

This vulnerability is an external control of file name or path (CWE-73) flaw where an unauthenticated attacker can inject arbitrary data into server files. By chaining the /3/Parse and /3/Frames/framename/export endpoints, an attacker can overwrite critical system files, such as SSH keys or configuration scripts.

The potential for remote code execution poses a catastrophic risk to organizational security, as it grants attackers the ability to compromise the entire host system. With a CVSS score of 9.1, this vulnerability signifies a high likelihood of total system compromise, leading to potential data exfiltration, loss of service, and severe reputational damage.

Immediate Action: Since a specific patch version is currently unconfirmed, administrators should restrict network access to the h2o-3 instance to trusted IP addresses only and disable the affected endpoints if possible.

Proactive Monitoring: Monitor server access logs for anomalous requests to the /3/Parse and /3/Frames endpoints, particularly those attempting to write to system-level directories.

Compensating Controls: Implement a Web Application Firewall (WAF) rule to block requests containing malicious file paths or suspicious header injections targeted at the h2o-3 API endpoints.

Public Exploit Available: Unknown.

Given the critical nature of this vulnerability and the potential for complete system takeover, organizations should treat this as a high-priority security incident. Organizations must immediately isolate the affected h2o-3 instances from the public internet and maintain a vigilant watch for vendor-released security updates to address the underlying file path control flaw.