CVE-2025-6544
Deserialization Vulnerability in h2oai/h2o-3
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Deserialization Vulnerability in h2oai/h2o-3
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.
- Record
CVE-2025-6544- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
EUVDEUVD-2025-30380
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.
- Record
EUVD-2025-30380- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-5w3j-gwgh-4rfv
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.
- Record
GHSA-5w3j-gwgh-4rfv- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2025-6544- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
OSV
Deserialization Vulnerability in h2oai/h2o-3
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.
- Record
CVE-2025-6544- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
OSVGHSA-5w3j-gwgh-4rfv
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.
- Record
GHSA-5w3j-gwgh-4rfv- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
OSVPYSEC-2026-349
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.
- Record
PYSEC-2026-349- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
ai.h2o:h2o-coreMaven |
through 3.46.0.7 | None known |
h2oPyPI |
through 3.46.0.7 | None known |
ai.h2o:h2o-coreMaven |
through 3.46.0.7, plus listed versions 0.1.100.1.110.1.120.1.130.1.14 Show 45 moreShow less0.1.150.1.160.1.170.1.180.1.190.1.200.1.210.1.220.1.230.1.240.1.250.1.30.1.3.10.1.40.1.50.1.60.1.80.1.90.2.3.50.2.3.60.3.0.23.0.0.123.0.0.163.0.0.183.0.0.193.0.0.223.0.0.253.0.0.263.0.0.303.0.0.53.0.0.83.0.1.23.0.1.33.0.1.43.10.0.13.10.0.103.10.0.23.10.0.33.10.0.43.10.0.53.10.0.63.10.0.73.10.0.83.10.0.93.10.1.1 |
None known |
h2oPyPI |
through 3.46.0.7, plus listed versions 3.10.0.103.10.0.33.10.0.63.10.0.73.10.0.8 Show 45 moreShow less3.10.3.33.10.3.43.10.4.13.10.4.23.10.4.33.10.4.43.10.4.63.10.4.83.16.0.13.16.0.23.16.0.33.16.0.43.18.0.13.18.0.103.18.0.113.18.0.23.18.0.33.18.0.43.18.0.53.18.0.63.18.0.73.18.0.83.18.0.93.20.0.43.20.0.53.20.0.63.20.0.73.20.0.83.22.0.13.22.0.23.22.0.33.22.0.43.22.0.53.22.1.13.22.1.23.22.1.33.22.1.43.22.1.53.22.1.63.24.0.13.24.0.23.24.0.33.24.0.43.24.0.53.26.0.1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2025-6544 is a critical vulnerability (CVSS 9.8) in H2o, published September 21, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.95%, the 61st percentile. No source names a fixed version.
References
huntr.com/bounties/53f35a0f-d644-4f82-93aa-89fe7e0aed40
github.com/h2oai/h2o-3/commit/0298ee348f5c73673b7b542158081e79605f5f25
nvd.nist.gov/vuln/detail/CVE-2025-6544
pypi.org/project/h2o
Left out here: 269 versions. The JSON record has them.