RCE in H2o
CVE-2026-3960
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.
Vulnerability class: RCE (Remote Code Execution)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.010 (62.4th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 62nd percentile — 62.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.009 · newest: 0.010 · change: +0.001
Affected products
- H2o
- H2oai H2oai/h2o-3 — versions unspecified
Weakness classification (CWE)
References
- huntr.com/bounties/6954fe04-b905-453f-8c53-205ac8377e0d (Exploit, Third Party Advisory)
- github.com/h2oai/h2o-3/commit/b9ae2d3c5220db2dc53753357a783e590364d044 (Patch)
Frequently asked questions
- What is CVE-2026-3960?
- CVE-2026-3960 is a critical-severity vulnerability in H2o, classified under Code Injection. CVSS score: 9.8/10. Published 2026-04-23.
- How severe is CVE-2026-3960?
- Critical severity. CVSS v3 base score is 9.8 out of 10.