9.8

CVSS Score

3.0

-

CVSS Score

Basic Information

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CVE-2025-6544

CVE-2025-6544: H2O affected by a deserialization vulnerability

A deserialization vulnerability exists in h2oai/h2o-3 versions <= 3.46.0.7, 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.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2025-6544

CVE-2025-6544:

9.8

CVSS Score

3.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
ai.h2o:h2o-core	maven	<= 3.46.0.7
h2o	pip	<= 3.46.0.7

Technical Details

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Root Cause Analysis

The vulnerability is a deserialization issue within H2O's JDBC functionality, identified as CVE-2025-6544. The root cause is the improper validation of JDBC connection strings in the water.jdbc.SQLManager.validateJdbcUrl function. The original code did not account for URL-encoded characters in the connection string, allowing attackers to bypass a regular expression-based filter for dangerous JDBC parameters. By double or multiple URL-encoding the payload, an attacker could smuggle malicious parameters, leading to arbitrary file reads and potentially remote code execution.

The provided patch for commit 0298ee348f5c73673b7b542158081e79605f5f25 clearly shows the remediation. The validateJdbcUrl function was modified to include a loop that repeatedly decodes the jdbcUrl string until no more decoding is possible. This ensures that any nested URL-encoded characters are revealed before the validation checks are applied. The vulnerable function is therefore water.jdbc.SQLManager.validateJdbcUrl, as it was the entry point for the malicious input and contained the flawed validation logic. Any runtime profile during exploitation would show this function being called with the malicious, encoded JDBC string.

Vulnerable functions

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WAF Protection Rules

WAF Rule

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Reasoning

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