CVE-2025-6544: Deserialization Vulnerability in h2oai/h2o-3
Vulnerability summary
CVE-2025-6544 is a critical (CVSS 9.8) Deserialization of Untrusted Data vulnerability in h2o. EPSS estimates a 0.95% chance of exploitation in the next 30 days, higher than 61.3% of scored vulnerabilities. 1 public exploit is recorded.
Public exploit (reference, Date unknown)
Source freshness unavailable
How is this decided?Timeline
- 21-09-2025PublishedVulnerability first disclosed.
- 22-09-2025Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · PypiEcosystem advisory · calculated9.8CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · MavenEcosystem advisory · calculated9.8CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- NVDNIST9.8CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.95%
Chance of exploitation in the next 30 days
Percentile
61%
Versus all other CVEs
30-day change
Increase +0.03 pp
From 0.92% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
1 foundExploit Reference (huntr.com)
Maturity: unknown
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ai.h2o1 product
- h2o-core≤ 3.46.0.7
H2o1 product
- h2o≥ 3.0.0.2, ≤ 3.46.0.8
H2oai1 product
- h2oai/h2o-3≥ unspecified, < 3.46.8
PyPI1 product
- h2o≤ 3.46.0.7
4 vendors · 4 products
References
7 links
- github.com/h2oai/h2o-3PACKAGE