CVE-2025-10769: H2O H2O-3 RCE Vulnerability

CVE-2025-10769 Overview

A deserialization vulnerability has been identified in h2oai h2o-3, an open-source distributed machine learning platform. The vulnerability affects the /99/ImportSQLTable endpoint within the H2 JDBC Driver component, where improper handling of the connection_url argument allows attackers to inject malicious serialized objects. This flaw enables remote attackers with low privileges to potentially compromise the confidentiality, integrity, and availability of affected systems through insecure deserialization attacks.

Critical Impact

Remote attackers can exploit this deserialization vulnerability via the network to potentially execute arbitrary code or manipulate application behavior through malicious serialized payloads targeting the H2 JDBC Driver's ImportSQLTable functionality.

Affected Products

• h2oai h2o-3 versions up to and including 3.46.08
• H2O Machine Learning Platform with H2 JDBC Driver component
• Systems utilizing the /99/ImportSQLTable endpoint

Discovery Timeline

• September 21, 2025 - CVE-2025-10769 published to NVD
• October 8, 2025 - Last updated in NVD database

Technical Details for CVE-2025-10769

Vulnerability Analysis

This vulnerability stems from insecure deserialization practices (CWE-502) combined with improper input validation (CWE-20) in the H2O-3 machine learning platform. The vulnerable component processes user-supplied data through the connection_url parameter without adequate validation or sanitization before deserialization operations occur. When exploited, this allows attackers to craft malicious serialized objects that, upon deserialization, can lead to arbitrary code execution or other security-compromising behaviors within the application context.

The vulnerability is accessible remotely over the network and requires only low-privilege authentication to exploit. The vendor was contacted regarding this vulnerability but did not respond, leaving users without an official security patch at the time of disclosure.

Root Cause

The root cause of CVE-2025-10769 lies in the lack of proper input validation and secure deserialization practices within the ImportSQLTable functionality. The connection_url argument is processed without sufficient checks, allowing attackers to pass crafted serialized data that gets deserialized by the application. Java deserialization vulnerabilities of this nature typically occur when untrusted input is directly passed to deserialization functions without validation of the object types being instantiated.

Attack Vector

The attack is executed remotely over the network by sending a crafted HTTP request to the /99/ImportSQLTable endpoint. An authenticated attacker with low privileges can manipulate the connection_url parameter to include malicious serialized Java objects. When the H2 JDBC Driver processes this input, the deserialization of the malicious payload can trigger arbitrary code execution or other unintended application behaviors.

The vulnerability has been publicly disclosed with proof-of-concept information available through security research channels. Technical details regarding the exploitation mechanism can be found in the GitHub PoC Issue and the Huntr Bounty Report.

Detection Methods for CVE-2025-10769

Indicators of Compromise

• Unusual HTTP requests to /99/ImportSQLTable endpoint with abnormally large or encoded connection_url parameters
• Unexpected Java serialization patterns in network traffic targeting H2O-3 instances
• Anomalous process spawning or file system activity following SQL import operations
• Log entries showing deserialization errors or unexpected class instantiation attempts

Detection Strategies

• Monitor HTTP traffic for requests to the /99/ImportSQLTable endpoint with suspicious connection_url values
• Implement application-level logging to detect deserialization attempts with non-standard object types
• Deploy network intrusion detection rules to identify Java serialized object patterns in web requests
• Configure SentinelOne Singularity Platform to monitor for behavioral indicators associated with deserialization attacks

Monitoring Recommendations

• Enable verbose logging on H2O-3 instances to capture all ImportSQLTable operations
• Implement network segmentation to restrict access to H2O-3 management endpoints
• Configure alerting for any unexpected outbound connections from H2O-3 server processes
• Regularly audit authentication logs for unauthorized access attempts to the affected endpoint

How to Mitigate CVE-2025-10769

Immediate Actions Required

• Restrict network access to the /99/ImportSQLTable endpoint to trusted IP addresses only
• Implement additional authentication and authorization controls for SQL import functionality
• Consider disabling the ImportSQLTable feature if not required for operations
• Deploy web application firewall (WAF) rules to filter potentially malicious connection_url parameters

Patch Information

At the time of publication, the vendor (h2oai) has not released an official security patch for this vulnerability. The vendor was contacted during the responsible disclosure process but did not respond. Users should monitor the official H2O-3 GitHub repository for future security updates and apply patches immediately when available.

Workarounds

• Implement network-level access controls to restrict access to H2O-3 administrative endpoints
• Deploy a reverse proxy with strict input validation rules to sanitize connection_url parameters before they reach the application
• Use Java security managers or deserialization filters to restrict which classes can be instantiated during deserialization
• Consider running H2O-3 in an isolated network environment with limited connectivity to reduce attack surface

# Example: Restrict access to ImportSQLTable endpoint using iptables
# Allow only trusted internal network (adjust IP range as needed)
iptables -A INPUT -p tcp --dport 54321 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 54321 -j DROP

# Example: Block suspicious requests using nginx reverse proxy
# Add to nginx server configuration
location /99/ImportSQLTable {
    # Limit access to trusted IPs
    allow 10.0.0.0/8;
    deny all;
    
    # Add request size limits
    client_max_body_size 1m;
}