CVE-2025-6544 json
Deserialization Vulnerability in h2oai/h2o-3
published 2025-09-21 13 mo ago modified 2026-10-27 12 d ago also GHSA-5w3j-gwgh-4rfv , PYSEC-2026-349 , EUVD-2025-30380
- cvss
- 9.8
- version 3.0, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.0%
- EPSS 1.0% chance of exploitation in 30 days, percentile 61%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- total
- Assessed
- 13 mo ago
Exploit prediction
0.95% chance of exploitation in the next 30 days, higher than 61% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- huntr.com https://huntr.com/bounties/53f35a0f-d644-4f82-93aa-89fe7e0aed40 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.0 | 9.8 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| GitHub | 3.0 | 9.8 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| OSV | 3.0 | 9.8 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| maven | ai.h2o:h2o-core | <=3.46.0.7 |
no fix listed |
| pypi | h2o | <=3.46.0.7 |
no fix listed |
Affected products
- h2oai h2oai/h2o-3
Classification
- Weakness
-
- CWE-502 Deserialization of Untrusted Data
References
-
github.com
/h2oai/h2o-3/commit/0298ee348f5c73673b7b542158081e79605f5f25
web, patch
-
huntr.com
/bounties/53f35a0f-d644-4f82-93aa-89fe7e0aed40
exploit, web, third-party-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2025-6544
advisory
-
github.com
/h2oai/h2o-3
package
-
github.com
/pypa/advisory-database/tree/main/vulns/h2o/PYSEC-2026-349.yaml
web
-
pypi.org
/project/h2o
web, package
-
github.com
/advisories/GHSA-5w3j-gwgh-4rfv
advisory
Sources
- CVE List CVE-2025-6544
- GitHub Advisory GHSA-5w3j-gwgh-4rfv
- NVD CVE-2025-6544
- OSV PYSEC-2026-349
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