CVE-2026-3960: Remote Code Execution in h2oai/h2o-3

Vulnerability summary

CVE-2026-3960 is a critical (CVSS 9.8) Improper Control of Generation of Code vulnerability in h2o. EPSS estimates a 0.94% chance of exploitation in the next 30 days, higher than 60.9% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 23-04-2026
   PublishedVulnerability first disclosed.
2. 23-04-2026
   Last modifiedVulnerability information updated.

Description

A critical remote code execution vulnerability exists in the unauthenticated REST API endpoint /99/ImportSQLTable in H2O-3 version 3.46.0.9 and prior. The vulnerability arises due to insufficient security controls in the parameter blacklist mechanism, which only targets MySQL JDBC driver-specific dangerous parameters. An attacker can bypass these controls by switching the JDBC URL protocol to jdbc:postgresql: and exploiting PostgreSQL JDBC driver-specific parameters such as socketFactory and socketFactoryArg. This allows unauthenticated attackers to execute arbitrary code on the H2O-3 server with the privileges of the H2O-3 process. The issue is resolved in version 3.46.0.10.

• CWE-94Improper Control of Generation of CodeThe product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.