CVE-2025-6507: Deserialization of Untrusted Data in h2oai/h2o-3

Severity: critical (CVSS 9.8 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 16.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-09-01 · updated 2026-06-17
Weakness: CWE-502

Description

A vulnerability in the h2oai/h2o-3 repository allows attackers to exploit deserialization of untrusted data, potentially leading to arbitrary code execution and reading of system files. This issue affects the latest master branch version 3.47.0.99999. The vulnerability arises from the ability to bypass regular expression filters intended to prevent malicious parameter injection in JDBC connections. Attackers can manipulate spaces between parameters to evade detection, allowing for unauthorized file access and code execution. The vulnerability is addressed in version 3.46.0.8.

Affected products

h2oai/h2o-3: before 3.46.0.8 — fixed in 3.46.0.8

How to fix

Upgrade to a fixed version: h2oai/h2o-3 3.46.0.8. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2025-6507 or the next vulnerability affects your stack