Answer in brief
CVE-2025-6544 records a Critical severity (CVSS 9.8) vulnerability in H2O affected by a deserialization vulnerability. The current sources do not mark it as known exploited. The current feed maps ai.h2o:h2o-core (maven), ai.h2o:h2o-core (maven), h2o (pip), h2o (pypi). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps ai.h2o:h2o-core (maven), ai.h2o:h2o-core (maven), h2o (pip), h2o (pypi). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:h2o:h2o:*:*:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| ai.h2o:h2o-coremaven | >=0 | Not reported |
| ai.h2o:h2o-coremaven | <=3.46.0.7 | Not reported |
| h2opip | <=3.46.0.7 | Not reported |
| h2opypi | >=0 | Not reported |
Published upstream
Sep 21, 2025
Evidence: source:ghsa:source_dates:source-dates:recordSource modified
Oct 27, 2026
Evidence: source:ghsa:source_dates:source-dates:recordFirst seen by HOL
Aug 8, 2026
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.
Quoted source text, attributed separately from HOL analysis.