Vulnerability · Published Sep 21, 2025 · Assigned by @huntr_ai

CVE-2025-6544Deserialization Vulnerability in h2oai/h2o-3

Critical 9.8

In plain English

A critical-severity unsafe deserialization in h2oai/h2o-3 from h2oai. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 61% of all known vulnerabilities).

Severity (CVSS 3.0)9.8Critical

Exploit odds (30 days)1.0%top 38.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

A deserialization vulnerability exists in h2oai/h2o-3 versions <= 3.46.0.8, allowing attackers to read arbitrary system files and execute arbitrary code. The vulnerability arises from improper handling of JDBC connection parameters, which can be exploited by bypassing regular expression checks and using double URL encoding. This issue impacts all users of the affected versions.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Maven	ai.h2o:h2o-core	no fix listed	GHSA-5w3j-gwgh-4rfv
PyPI	h2o	no fix listed	PYSEC-2026-349
PyPI	h2o	no fix listed	GHSA-5w3j-gwgh-4rfv

Affected products (as reported)

Vendor	Product	Versions
h2oai	h2oai/h2o-3	unspecified – before 3.46.8

Weakness: CWE-502 · Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

In plain English

Official description

Affected packages & fixed versions

Affected products (as reported)

References