H2O-3 is Vulnerable to Code Injection

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-3960: 0.94% estimated exploitation activity in the next 30 days; percentile 60.93 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

23 Apr 2026, 10:16 UTC

Last modified by the source

13 Jul 2026, 07:26 UTC

Source last checked

26 Oct 2026, 16:45 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-qmcv-hh7c-3m56

2. Revision 1 · created · 24 Oct 2026

   Published from osv record PYSEC-2026-2180

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# Patch Next advisory brief: CVE-2026-3960

Advisory: H2O-3 is Vulnerable to Code Injection
IDs: CVE-2026-3960, GHSA-qmcv-hh7c-3m56
Record: https://patchnext.com/advisories/cve-2026-3960 (revision 2, source checked 26 Oct 2026, 16:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: h2o 3.46.0.10; ai.h2o:h2o-core 3.46.0.10. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI h2o: affected < 3.46.0.10; fixed in 3.46.0.10
- Maven ai.h2o:h2o-core: affected < 3.46.0.10; fixed in 3.46.0.10

## Suggested inspection (read-only)
- `python -m pip show h2o`: prints the installed version. Run with the environment that serves production active.
- Maven ai.h2o:h2o-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on h2o, ai.h2o:h2o-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/PYSEC-2026-2180 (OSV record PYSEC-2026-2180 lists affected ranges: PyPI h2o >=0 <3.46.0.10 (fixed))
- Verified: https://github.com/advisories/GHSA-qmcv-hh7c-3m56 (GitHub-reviewed advisory GHSA-qmcv-hh7c-3m56 lists affected ranges: Maven ai.h2o:h2o-core >=0 <3.46.0.10)

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