What’s Vulnerable › Vulnerabilities

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

• Severity: critical (CVSS 9.8 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-09-21 · updated 2026-10-05
• Weakness: CWE-502

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 products

• h2oai/h2o-3: from 3.0.0.2 through 3.46.0.8

References

• https://github.com/h2oai/h2o-3/commit/0298ee348f5c73673b7b542158081e79605f5f25
• https://huntr.com/bounties/53f35a0f-d644-4f82-93aa-89fe7e0aed40
• https://huntr.com/bounties/53f35a0f-d644-4f82-93aa-89fe7e0aed40

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