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

What is CVE-2026-3960?

CVE-2026-3960 is a medium-severity code injection vulnerability in h2oai/h2o-3, published on 23 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-94

Which versions are affected by CVE-2026-3960?

3 open source packages ship an affected version, including ai.h2o:h2o-core and h2o. It affects 1 product.

Products include H2o H2o.

How do I fix CVE-2026-3960?

Upgrade ai.h2o:h2o-core to 3.46.0.10 or later.

Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.

Is CVE-2026-3960 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3960 exists.

Other vulnerabilities in h2oai/h2o-3

• CVE-2023-6016 H2O Remote Code Execution via POJO Model Import Critical 10.0
• CVE-2025-6544 Deserialization Vulnerability in h2oai/h2o-3 Critical 9.8
• CVE-2024-10553 Jdbc Deserialization in h2oai/h2o-3 Critical 9.8
• CVE-2023-6569 External Control of File Name or Path in h2oai/h2o-3 Critical 9.3
• CVE-2023-6013 H2O Local File Include Critical 9.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-qmcv-hh7c-3m56, PYSEC-2026-2180.