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H2O CVE-2025-6544

CRITICAL
Deserialization of Untrusted Data (CWE-502)
2025-09-21 security@huntr.dev
RCE Deserialization H2O
9.8
CVSS 3.0 · NVD
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Severity by source

NVD PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Analysis Generated
Mar 28, 2026 - 19:13 vuln.today
Patch released
Mar 28, 2026 - 19:13 nvd
Patch available
PoC Detected
Oct 08, 2025 - 20:05 vuln.today
Public exploit code
CVE Published
Sep 21, 2025 - 09:15 nvd
CRITICAL 9.8

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 20 maven packages depend on ai.h2o:h2o-core (20 direct, 0 indirect)
  • 3 pypi packages depend on h2o (3 direct, 0 indirect)

Ecosystem-wide dependent count for version 3.46.0.7 and other introduced versions.

DescriptionCVE.org

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.

AnalysisAI

A deserialization vulnerability exists in h2oai/h2o-3 versions <= 3.46.0.8, allowing attackers to read arbitrary system files and execute arbitrary code. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

Technical ContextAI

This vulnerability is classified as Deserialization of Untrusted Data (CWE-502), which allows attackers to execute arbitrary code through malicious serialized objects. 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 products include: H2O.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Avoid deserializing untrusted data. Use safe serialization formats (JSON). Implement integrity checks and type allowlists.

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CVE-2025-6544 vulnerability details – vuln.today
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